Host board, optical receiver, optical transmitter, optical transceiver, and method of mounting optical transceiver on host board

A host board for mounting an optical transceiver includes a connector that is configured to attach thereto and detach therefrom an optical transceiver having at least one lane and includes electrical contacts as many as the at least one lane, a management unit configured to receive lane information regarding the at least one lane of the optical transceiver from the optical transceiver through the connector and specify an available electrical contact, and a communication unit configured to communicate with the optical transceiver through the connector. The communication unit is configured to communicate information with the optical transceiver through the electrical contact specified by the management unit.

TECHNICAL FIELD

The present invention relates to a host board, an optical receiver, an optical transmitter, an optical transceiver, and a method of mounting an optical transceiver on a host board. The present application claims a priority based on Japanese Patent Application No. 2016-166111 filed on Aug. 26, 2016 and Japanese Patent Application No. 2016-236075 filed on Dec. 5, 2016, the entire contents of which are incorporated herein by reference.

BACKGROUND ART

The transmission capacity in optical communications has been dramatically increased. In recent years, optical communications having a transmission capacity of 40 Gbps or 100 Gbps have been proposed. For example, in optical communications of 40 Gbps, four optical signals having a rate of 10 Gbps and different wavelengths are multiplexed. In optical communications of 100 Gbps, four optical signals of 25 Gbps or ten optical signals of 10 Gbps are multiplexed.

In order to achieve a transmission capacity of 40 Gbps or 100 Gbps, the transmission capacity of the optical transceiver has been expanded. For example, “CFP MSA CFP4 Hardware Specification, Revision 1.1” (NPL 1) discloses an optical transceiver for supporting a 40 Gbps interface and a 100 Gbps interface for, for example, Ethernet (registered trademark) and telecommunications.

For example, US Patent Application Publication No. 2016/0149643 (PTL 1) discloses an optical transceiver including an integration of four optical devices each having a transmission rate of 10 Gbps. The optical transceiver multiplexes four optical signals having different wavelengths to equivalently obtain transmission rates of 40 Gbps and 100 Gbps. For example, US Patent Application Publication No. 2011/0103797 (PTL 2) discloses an optical transceiver including four separate optical devices.

CITATION LIST

Patent Literature

PTL 1: US Patent Application Publication No. 2016/0149643PTL 2: US Patent Application Publication No. 2011/0103797

Non Patent Literature

SUMMARY OF INVENTION

A host board according to an aspect of the present invention is a host board for mounting an optical transceiver, and includes a connector, a management unit, and a communication unit. The connector is configured to attach thereto and detach therefrom the optical transceiver having at least one lane and includes at least one electrical contact as many as the at least one lane. The management unit is configured to receive lane information regarding the at least one lane of the optical transceiver from the optical transceiver through the connector and specify the at least one electrical contact that is available. The communication unit is configured to communicate with the optical transceiver through the connector. The communication unit is configured to communicate information with the optical transceiver through the at least one electrical contact specified by the management unit.

An optical receiver according to an aspect of the present invention includes a wavelength demultiplexing, at least one optical reception unit, an interface, and a communication unit. The wavelength demultiplexing unit is configured to demultiplex at least one optical signal to be received from an optical signal transmitted through an optical fiber and subjected to wavelength multiplexing. The at least one optical reception unit is configured to receive the at least one optical signal to be received and output an electric signal. The interface includes an electrical contact for outputting the electric signal from the at least one optical reception unit to a host board. The communication unit is configured to notify the host board of information for specifying an electrical contact available for transmitting the electric signal from the at least one optical reception unit to the host board and the at least one optical reception unit.

An optical transmitter according to an aspect of the present invention includes at least one optical transmission unit, a wavelength multiplexing unit, an interface, and a communication unit. The at least one optical transmission unit is configured to receive an electric signal from a host board and transmit at least one optical signal having an identical wavelength or different wavelengths. The wavelength multiplexing unit is configured to transmit the at least one optical signal from the at least one optical transmission unit to an optical fiber, and when the at least one optical signal from the at least one optical transmission unit has different wavelengths, transmit an optical signal subjected to wavelength multiplexing to the optical fiber. The interface includes an electrical contact for receiving an electric signal from the host board. The communication unit is configured to notify the host board of information for specifying the electrical contact available for transmitting the electric signal from the host board to the at least one optical transmission unit and the at least one optical transmission unit.

An optical transceiver according to an aspect of the present invention includes a wavelength demultiplexing unit, a wavelength multiplexing unit, at least one optical reception unit, at least one optical transmission unit, an interface, and a communication unit. The wavelength demultiplexing unit is configured to demultiplex at least one optical signal to be received from an optical signal transmitted through an optical fiber and subjected to wavelength multiplexing. The wavelength multiplexing unit is integral with the wavelength demultiplexing unit or separate from the wavelength demultiplexing unit. The at least one optical reception unit is configured to receive the at least one optical signal to be received. The at least one optical transmission unit is configured to receive an electric signal from a host board and output an optical signal. The interface has a first electrical contact for receiving an electric signal from the host board, and a second electrical contact for outputting an electric signal from the at least one optical reception unit to the host board. The communication unit is configured to notify the host board of information for specifying the at least one optical reception unit, the at least one optical transmission unit, the first electrical contact available for transmitting the electric signal from the host board to the at least one optical transmission unit, and the second electrical contact available for transmitting the electric signal from the at least one optical reception unit to the host board.

A method of mounting an optical transceiver on a host board according to an aspect of the present invention includes connecting an optical transceiver storing lane information to a connector of a host board, reading the lane information from the optical transceiver, determining the number of lanes based on the lane information, and performing control for multi-lane distribution based on the number of lanes.

A host board according to an aspect of the present invention is a host board for mounting an optical transceiver, and includes a connector, a management unit, and a communication unit. The connector is configured to attach thereto and detach therefrom the optical transceiver having at least one lane. The management unit is configured to receive lane information regarding an available lane of the optical transceiver from the optical transceiver through the connector and specify the available lane. The communication unit is configured to communicate with the optical transceiver through the connector. The communication unit is configured to communicate data with the optical transceiver. The data is transmitted through the available lane specified by the management unit.

An optical receiver according to an aspect of the present invention includes a wavelength demultiplexing unit, at least one optical reception unit, an interface, and a communication unit. The wavelength demultiplexing unit is configured to demultiplex at least one optical signal to be received from an optical signal transmitted through an optical fiber and subjected to wavelength multiplexing. The at least one optical reception unit is configured to receive the at least one optical signal to be received and output an electric signal. The interface is provided for outputting an electric signal from the at least one optical reception unit to a host board. The communication unit is configured to notify the host board of information for specifying a lane available for transmitting the electric signal from the at least one optical reception unit to the host board and the at least one optical reception unit.

An optical transmitter according to an aspect of the present invention includes at least one optical transmission unit, a wavelength multiplexing unit, an interface, and a communication unit. The at least one optical transmission unit is configured to receive an electric signal from a host board and transmit at least one optical signal having an identical wavelength or different wavelengths. The wavelength multiplexing unit is configured to transmit the at least one optical signal from the at least one optical transmission unit to an optical fiber, and when the at least one optical signal from the at least one optical transmission unit has different wavelengths, transmit an optical signal subjected to wavelength multiplexing to the optical fiber. The interface is provided for receiving an electric signal from the host board. The communication unit is configured to notify the host board of information for specifying a lane available for transmitting the electric signal from the host board to the at least one optical transmission unit and the at least one optical transmission unit.

An optical transceiver according to an aspect of the present invention includes a wavelength demultiplexing unit, a wavelength multiplexing unit, at least one optical reception unit, at least one optical transmission unit, an interface, and a communication unit. The wavelength demultiplexing unit is configured to demultiplex at least one optical signal to be received from an optical signal transmitted through an optical fiber and subjected to wavelength multiplexing. The wavelength multiplexing unit is integral with the wavelength demultiplexing unit or separate from the wavelength demultiplexing unit. The at least one optical reception unit is configured to receive the at least one optical signal to be received. The at least one optical transmission unit is configured to receive an electric signal from a host board and output an optical signal. The interface is provided for receiving an electric signal from the host board and outputting an electric signal from the at least one optical reception unit to the host board. The communication unit is configured to notify the host board of information for specifying the at least one optical reception unit, the at least one optical transmission unit, and a lane available for transmitting the electric signal from the host board to the at least one optical transmission unit and transmitting the electric signal from the at least one optical reception unit to the host board.

DETAILED DESCRIPTION

Problem to be Solved by the Present Disclosure

For example, in Ethernet (registered trademark) passive optical network (EPON), 25 G, 50 G, and 100 G-EPONs have been standardized (IEEE P802.3ca). It is conceivable that as a scenario for introducing the above, transmission capacity may be expanded (upgraded) incrementally.

Each of the above literatures discloses an optical transceiver capable of achieving a specific transmission capacity (e.g., 40 Gbps). Each literature, however, does not specifically disclose incremental changes in transmission capacity.

An object of the present disclosure is to provide configurations of an optical transceiver and a host board for optical communications in which transmission capacity can be incrementally changed.

Description of Embodiments

Embodiments of the present invention will initially be listed and described.

(1) A host board according to an aspect of the present invention is a host board for mounting an optical transceiver, and includes a connector, a management unit, and a communication unit. The connector is configured to attach thereto and detach therefrom the optical transceiver having at least one lane and includes at least one electrical contact as many as the at least one lane. The management unit is configured to receive lane information regarding the at least one lane of the optical transceiver from the optical transceiver through the connector and specify the at least one electrical contact that is available. The communication unit is configured to communicate with the optical transceiver through the connector. The communication unit is configured to communicate information with the optical transceiver through the at least one electrical contact specified by the management unit.

According to the above, a host board for optical communications can be provided that can incrementally change transmission capacity. The management unit specifies an available electrical contact of a connector based on the lane information from the optical transceiver. The transmission capacity can be changed by changing the number of lanes. The number of lanes can be changed by specifying an available electrical contact. Consequently, the transmission capacity can be incrementally changed.

(2) Preferably, the lane information includes at least one of information indicating whether each of the at least one lane is implemented and information regarding a wavelength of an optical signal transmitted through the at least one lane.

According to the above, the management unit can determine the number of lanes. Further, the management unit can recognize a combination of lanes capable of wavelength multiplexing, not time division multiplexing on the same optical fiber, based on, for example, information regarding wavelengths.

(3) Preferably, the lane information includes information regarding a transmission capacity of the optical transceiver. The management unit is configured to determine the number of the lanes based on the information regarding the transmission capacity to specify the at least one electrical contact that is available.

According to the above, the management unit can specify an available electrical contact from the information on the transmission capacity supported by the optical transceiver.

(4) Preferably, the connector includes the at least one electrical contacts as many as four of the lanes.

According to the above, for example, parallel transmission by four lanes is enabled. In one example, a transmission capacity of 40 Gbps (10 G×4) or 100 Gbps (25 G×4) is enabled.

(5) Preferably, the at least one lane includes a first lane for a first transmission capacity of the optical transceiver and a second lane for a second transmission capacity of the optical transceiver. The second transmission capacity differs from the first transmission capacity.

According to the above, the optical transceiver that can achieve both the first transmission capacity and the second transmission capacity is connected to the host board. This allows coexistence of a previous generation system having low transmission capacity and a new generation system having high transmission capacity.

(6) Preferably, the management unit is configured to detect connection of the optical transceiver to the connector and read the lane information from the optical transceiver.

According to the above, plug-in to the host board by the optical transceiver can change the number of lanes, easily changing transmission capacity.

(7) An optical receiver according to an aspect of the present invention includes a wavelength demultiplexing unit, at least one optical reception unit, an interface, and a communication unit. The wavelength demultiplexing unit is configured to demultiplex at least one optical signal to be received from an optical signal transmitted through an optical fiber and subjected to wavelength multiplexing. The at least one optical reception unit is configured to receive the at least one optical signal to be received and output an electric signal. The interface includes an electrical contact for outputting the electric signal from the at least one optical reception unit to a host board. The communication unit is configured to notify the host board of information for specifying an electrical contact available for transmitting an electric signal from the at least one optical reception unit to the host board and the at least one optical receiver.

According to the above, an optical receiver for optical communications can be provided that can incrementally change transmission capacity. The host board can specify an electrical contact for receiving an electric signal from the optical receiver based on the information from the optical receiver. Further, even when receiving a wavelength multiplexed signal corresponding to a transmission capacity that is not supported, the optical receiver can ignore an optical signal with a wavelength irrelevant to data to be transmitted.

(8) Preferably, the information includes at least one of information indicating whether each of a plurality of lanes is implemented and information regarding a wavelength of an optical signal transmitted through the at least one lane.

According to the above, the optical receiver can provide the host board with information by which the number of lanes can be determined. Further, the optical receiver notifies the host board of the information regarding the wavelength of an optical signal, allowing the host board to recognize a combination of lanes capable of, for example, wavelength multiplexing, not time division multiplexing on the same optical fiber.

(9) Preferably, the plurality of lanes include a first lane for a first transmission capacity of the optical receiver and a second lane for a second transmission capacity of the optical receiver. The second transmission capacity differs from the first transmission capacity.

According to the above, an optical receiver that can achieve both the first transmission capacity and the second transmission capacity is connected to the host board. This allows coexistence of a previous generation system having low transmission capacity and a new generation system having high transmission capacity.

(10) Preferably, the information includes information regarding a transmission capacity of the optical receiver.

According to the above, the information regarding a transmission capacity supported by the optical receiver can be provided to the host board. Consequently, the host board can determine the number of lanes and specify an available electrical contact.

(11) An optical transmitter according to an aspect of the present invention includes at least one optical transmission unit, a wavelength multiplexing unit, an interface, and a communication unit. The at least one optical transmission unit is configured to receive an electric signal from a host board and transmit at least one optical signal having an identical wavelength or different wavelengths. The wavelength multiplexing unit is configured to transmit the at least one optical signal from the at least one optical transmission unit to an optical fiber, and when the at least one optical signal from the at least one optical transmission unit has different wavelengths, transmit an optical signal subjected to wavelength multiplexing to the optical fiber. The interface includes an electrical contact for receiving an electric signal from the host board. The communication unit is configured to notify the host board of information for specifying the electrical contact available for transmitting the electric signal from the host board to the at least one optical transmission unit and the at least one optical transmission unit.

According to the above, an optical transmitter for optical communications can be provided that can incrementally change transmission capacity. The host board can specify an electrical contact for receiving an electric signal from the host board based on the information from the optical transmitter.

(12) Preferably, the information includes at least one of information indicating whether each of a plurality of lanes is implemented and information regarding a wavelength of an optical signal transmitted through each of the lanes.

According to the above, the optical transmitter can provide the host board with information by which the number of lanes can be determined. Further, the optical transmitter notifies the host board of the information regarding the wavelength of an optical signal, allowing the host board to recognize a combination of lanes capable of, for example, wavelength multiplexing, not time division multiplexing on the same optical fiber.

(13) Preferably, the plurality of lanes include a first lane for a first transmission capacity of the optical transmitter, and a second lane for a second transmission capacity of the optical transmitter. The second transmission capacity differs from the first transmission capacity.

According to the above, the optical transmitter that can achieve both the first transmission capacity and the second transmission capacity is connected to the host board. This allows coexistence of a previous generation system having low transmission capacity and a new generation system having high transmission capacity.

(14) Preferably, the information includes information regarding a transmission capacity of the optical receiver.

According to the above, the information regarding a transmission capacity supported by the optical receiver can be provided to the host board. Consequently, the host board can determine the number of lanes and specify an available electrical contact.

(15) An optical transceiver according to an aspect of the present invention includes a wavelength demultiplexing unit, a wavelength multiplexing unit, at least one optical reception unit, at least one optical transmission unit, an interface, and a communication unit. The wavelength demultiplexing unit is configured to demultiplex at least one optical signal to be received from an optical signal transmitted through an optical fiber and subjected to wavelength multiplexing. The wavelength multiplexing unit is integral with the wavelength demultiplexing unit or separate from the wavelength demultiplexing unit. The at least one optical reception unit is configured to receive the at least one optical signal to be received. The at least one optical transmission unit is configured to receive an electric signal from a host board and output an optical signal. The interface has a first electrical contact for receiving an electric signal from the host board and a second electrical contact for outputting an electric signal from the at least one optical reception unit to the host board. The communication unit is configured to notify the host board of information for specifying the at least one optical reception unit, the at least one optical transmission unit, the first electrical contact available for transmitting the electric signal from the host board to the at least one optical transmission unit, and the second electrical contact available for transmitting the electric signal from the at least one optical reception unit to the host board.

According to the above, the optical transceiver for incrementally changing transmission capacity can be provided.

(16) A method of mounting an optical transceiver on a host board according to an aspect of the present invention includes connecting an optical transceiver storing lane information to a connector of a host board, reading the lane information from the optical transceiver, determining the number of lanes based on the lane information, and performing control for multi-lane distribution based on the number of lanes.

According to the above, the number of lanes can be determined every time the optical transceiver is connected to the connector. Consequently, transmission capacity can be incrementally changed.

(17) Preferably, the method further includes connecting another optical transceiver having a transmission capacity higher than that of the optical transceiver to the connector in place of the optical transceiver.

According to the above, the transmission capacity can be changed by exchanging an optical transceiver connected to the connector of the host board.

(18) Preferably, the method further includes connecting another optical transceiver to the connector in place of the optical transceiver. The other optical transceiver has a first transmission capacity identical to a transmission capacity of the optical transceiver and a second transmission capacity higher than the transmission capacity of the optical transceiver.

According to the above, the optical transceiver that can achieve both the first transmission capacity and the second transmission capacity is connected to the host board. This allows coexistence of a previous generation system having low transmission capacity and a new generation system having high transmission capacity.

(19) A host board according to an aspect of the present invention is a host board for mounting an optical transceiver, and includes a connector, a management unit, and a communication unit. The connector is configured to attach thereto and detach therefrom the optical transceiver having at least one lane. The management unit is configured to receive lane information regarding a lane available to the optical transceiver from the optical transceiver through the connector and specify the lane that is available. The communication unit is configured to communicate with the optical transceiver through the connector. The communication unit is configured to communicate data with the optical transceiver. The data is transmitted through the available lane specified by the management unit.

According to the above, a host board for optical communications can be provided that can incrementally change transmission capacity. The management unit specifies an available lane based on the lane information from the optical transceiver. The transmission capacity can be changed by changing the number of lanes. The number of lanes can be changed by specifying an available lane. Consequently, the transmission capacity can be incrementally changed.

(20) An optical receiver according to an aspect of the present invention includes a wavelength demultiplexing unit, at least one optical reception unit, an interface, and a communication unit. The wavelengthdemultiplexing unit is configured to demultiplex at least one optical signal to be received from an optical signal transmitted through an optical fiber and subjected to wavelength multiplexing. The at least one optical reception unit is configured to receive the at least one optical signal to be received and output an electric signal. The interface is provided for outputting an electric signal from the at least one optical reception unit to a host board. The communication unit is configured to notify the host board of information for specifying a lane available for transmitting an electric signal from the at least one optical reception unit to the host board and the at least one optical reception unit.

According to the above, an optical receiver for optical communications can be provided that can incrementally change transmission capacity. The host board can specify a lane available for receiving an electric signal from the optical receiver based on the information from the optical receiver. Further, even when receiving a wavelength multiplexed signal corresponding to a transmission capacity that is not supported, the optical receiver can ignore an optical signal with a wavelength irrelevant to data to be transmitted.

(21) An optical transmitter according to an aspect of the present invention includes at least one optical transmission unit, a wavelength multiplexing unit, an interface, and a communication unit. The at least one optical transmission unit is configured to receive an electric signal from a host board and transmit at least one optical signal having an identical wavelength or different wavelengths. The wavelength multiplexing unit is configured to transmit the at least one optical signal from the at least one optical transmission unit to an optical fiber, and when the at least one optical signal from the at least one optical transmission unit has different wavelengths, transmit an optical signal subjected to wavelength multiplexing to the optical fiber. The interface is provided for receiving an electric signal from the host board. The communication unit is configured to notify the host board of information for specifying a lane available for transmitting the electric signal from the host board to the at least one optical transmission unit and the at least one optical transmission unit.

According to the above, an optical transmitter for optical communications can be provided that can incrementally change transmission capacity. The host board can specify a lane available for receiving an electric signal from the optical transmission unit based on the information from the optical transmitter.

(22) An optical transceiver according to an aspect of the present invention includes a wavelength demultiplexing unit, a wavelength multiplexing unit, at least one optical reception unit, at least one optical transmission unit, an interface, and a communication unit. The wavelength demultiplexing unit is configured to demultiplex at least one optical signal to be received from an optical signal transmitted through an optical fiber and subjected to wavelength multiplexing. The wavelength multiplexing unit is integral with the wavelength demultiplexing unit or separate from the wavelength demultiplexing unit. The at least one optical reception unit is configured to receive the at least one optical signal to be received. The at least one optical transmission unit is configured to receive an electric signal from a host board and output an optical signal. The interface is provided for receiving an electric signal from the host board and outputting an electric signal from the at least one optical reception unit to the host board. The communication unit is configured to notify the host board of information for specifying the at least one optical reception unit, the at least one optical transmission unit, and a lane available for transmitting the electric signal from the host board to the at least one optical transmission unit and transmitting the electric signal from the at least one optical reception unit to the host board.

According to the above, an optical transceiver for enabling incremental change of transmission capacity can be provided.

Detailed Description of Embodiments

Embodiments of the present invention will be described hereinafter with reference to the drawings. The same or corresponding elements in the drawings have the same reference numerals allotted, and description thereof will not be repeated.

FIG. 1shows an example configuration of an optical communication system according to an embodiment. InFIG. 1, a passive optical network (PON) system300is an optical communication system according to an embodiment. PON system300includes an optical line terminal (OLT)301, optical network units (ONUs)302, a PON line303, and an optical splitter304.

Optical line terminal301is placed in an office of a communication common carrier. Optical line terminal301has a host board (not shown) mounted therein. The host board is connected with an optical transceiver (not shown) that converts an electric signal and an optical signal to each other.

Optical network unit302is installed on the user side. Each of optical network units302is connected to optical line terminal301through PON line303.

PON line303is an optical communication line composed of optical fibers. PON line303includes a trunk optical fiber305and at least one branch optical fiber306. Optical splitter304is connected to trunk optical fiber305and branch optical fiber306. Optical network units302can be connected to PON line303.

An optical signal transmitted from optical line terminal301passes through PON line303and is branched to optical network units302by optical splitter304. On the other hand, the respective optical signals transmitted from optical network units302are bundled by optical splitter304and pass through PON line303to be transmitted to optical line terminal301. Optical splitter304passively branches or multiplexes signals input thereto, without requiring a specific external power supply.

PON system300is a point-to-multipoint (P2MP) system. The optical communication system according to an embodiment of the present invention may be a peer to peer (P2P) system.

As a high-rate PON system, a wavelength multiplexing PON system is studied which allocates a plurality of wavelengths to an upstream signal or a downstream signal and subjects the plurality of wavelengths to wavelength multiplexing to form an upstream signal or a downstream signal. For example, a 100 Gbps class PON can be configured to allocate a signal with a transmission capacity of 25 Gbps per wavelength to each of upstream and downstream and subject these wavelengths to wavelength multiplexing. As a scenario to introduce such a wavelength multiplexing PON system, incremental expansion (upgrade) of transmission capacity is conceivable. In the drawings described below, “Day 1”, “Day 2”, “Day 3”, and the like each indicate a stage of transmission capacity expansion. Here, the name indicating a stage of transmission capacity expansion is not particularly limited. For example, a stage may be represented as “first generation” or “second generation” using the term “generation”.

As shown inFIGS. 2 to 4, one scenario of transmission capacity expansion is addition of an optical transceiver. With reference toFIG. 2, a host board1is mounted on optical line terminal301(seeFIG. 1) and has ports11to14, an electrical processing large scale integrated circuit (LSI)2, and a concentration LSI3. Each of ports11to14is configured to receive and output a signal and data from and to the optical transceiver. Each port is implemented by a connector.

Each of ports11to14is configured to be connected with an optical transceiver101for 25 Gbps. At the stage of “Day 1”, optical transceiver101is connected only to port11.

Electrical processing LSI2communicates information with host board1externally. Electrical processing LSI2performs various types of processing on an electric signal output from optical transceiver101. Further, electrical processing LSI2receives an electric signal externally from host board1through concentration LSI3and generates an electric signal to be input to optical transceiver101. Concentration LSI3accommodates a plurality of transmission lines for electric signals.

Electrical processing LSI2supports multi-lane distribution control. In one embodiment, electrical processing LSI2can achieve transmission of 100 Gbps by four 25 Gbps lanes. By changing the number of lanes, electrical processing LSI2supports transmission rates of 25 Gbps, 50 Gbps, and 100 Gbps.

Optical transceiver101receives an optical signal from optical network unit302and converts the optical signal into an electric signal. The electric signal is output from optical transceiver101through port11to electrical processing LSI2. In contrast, optical transceiver101receives an electric signal from electrical processing LSI2through port11and converts the electric signal into an optical signal. The optical signal is transmitted from optical transceiver101through a PON line (seeFIG. 1) to optical network unit302.

FIG. 3shows a stage (Day 2) at which the transmission capacity has been expanded to 50 Gbps from the stage shown inFIG. 2. With reference toFIGS. 2 and 3, at the stage of “Day 2”, an optical transceiver102for 25 Gbps is mounted on host board1in addition to optical transceiver101. Optical transceiver102is connected to port12.

Optical transceiver101and optical transceiver102differ from each other in the wavelength of an optical signal. Optical wavelength multiplexer/demultiplexer (WM)31multiplexes an optical signal with a wavelength λ1 transmitted from optical transceiver101and an optical signal with a wavelength λ2 transmitted from optical transceiver102. The optical signal subjected to wavelength multiplexing is transmitted to optical network unit302. On the other hand, optical wavelength multiplexer/demultiplexer31demultiplexes an optical signal subjected to wavelength multiplexing transmitted from optical network unit302into two optical signals. Each of optical transceivers101and102receives a corresponding optical signal from optical wavelength multiplexer/demultiplexer31.

FIG. 4shows a stage (Day 3) at which the transmission capacity has been expanded to 100 Gbps from the stage shown inFIG. 3. With reference toFIGS. 3 and 4, at the stage of “Day 3”, four optical transceivers (optical transceivers101,102,103,104) for 25 Gbps are mounted on host board1. Optical transceivers103and104are connected to ports13and14, respectively. Optical wavelength multiplexer/demultiplexer31multiplexes an optical signal with a wavelength λ3 transmitted from optical transceiver103and an optical signal with a wavelength λ4 transmitted from optical transceiver104, in addition to the optical signals from optical transceivers101and102. On the other hand, optical wavelength multiplexer/demultiplexer31demultiplexes an optical signal subjected to wavelength multiplexing, transmitted from optical network unit302, into four optical signals. Each of optical transceivers101to104receives a corresponding optical signal from optical wavelength multiplexer/demultiplexer31.

To implement the scenario shown inFIGS. 2 to 4, the following points need to be considered. First, a plurality of ports have to be mounted on host board1for expected future use. On the other hand, at the stage of Day 1, only one port is used and three ports are unused. At the stage of Day 1, however, the unused ports are wasted. Further, since the transmission capacity is expanded by the four ports prepared in Day 1, the transmission capacity per host board is small.

Second, in expanding the transmission capacity (during a shift from Day 1 to Day 2), optical wavelength multiplexer/demultiplexer31needs to be installed. This leads to a strong possibility that optical wavelength multiplexer/demultiplexer31may be installed separately from optical line terminal301. However, securing the space for installing optical wavelength multiplexer/demultiplexer31may be difficult.

Third, in expanding the transmission capacity, an added optical transceiver and optical wavelength multiplexer/demultiplexer31need to be connected to each other by an optical fiber. Consequently, wiring of optical fibers tends to be complicated.

From the above points, Embodiment 1 can adopt the following scenario.FIG. 5shows a configuration of a host board according to an embodiment. With reference toFIG. 5, host board1includes port11, electrical processing LSI2, and concentration LSI3. Port11is configured to allow each of optical transceiver101, optical transceiver121, and optical transceiver111to be attached thereto and detached therefrom. Optical transceiver121has four channels with 25 Gbps and wavelength λ1. Optical transceiver111is an optical transceiver with 25 Gbps×4 wavelengths (λ1, λ2, λ3, λ4).

The optical transceiver according to an embodiment of the present invention is connected to port11to output, to electrical processing LSI2, information regarding the transmission capacity supported by the optical transceiver. Electrical processing LSI2acquires the information through port11. Used as a communication protocol between the optical transceiver and host board1is, for example, management data input/output (MDIO), serial peripheral interface (SPI), and serial communication such as I2C.

FIG. 6schematically shows a configuration regarding the electric connection between the optical transceiver, port11, and electrical processing LSI2. InFIG. 6, an optical transceiver111is representatively shown as an optical transceiver connectable to port11. Port11is implemented by a connector. The connector has electrical contacts4a,4b,4c,4d,6a,6b,6c,6d, and8.

Optical transceiver111includes an electrical interface43. Electrical interface43has pins43ato43i. With optical transceiver111connected to the connector (port11), pins43ato43iare electrically connected to electrical contacts4ato4d,6ato6d, and8, respectively. The pins of optical transceiver111may be arranged in accordance with, for example, centum gigabit form factor pluggable multi-source agreement (CFP MSA). In one embodiment, the optical transceiver may adhere to a standard referred to as CFP4.

High-rate signal lines5a,5b,5c,5d,7a,7b,7c, and7d, and control signal line9are connected to electrical processing LSI2. High-rate signal lines5a,5b,5c, and5dform one pair, and high-rate signal lines7a,7b,7c, and7dform another pair. The high-rate signal lines of one of the two pairs are used for transmission of an electric signal from the optical transceiver connected to the connector (port11) to electrical processing LSI2. The high-rate signal lines of the other pair are used for transmission of an electric signal from electrical processing LSI2to the optical transceiver.

One signal line of each pair corresponds to one lane. Thus, for optical transceiver101, one of high-rate signal lines5a,5b,5c, and5dand one of high-rate signal lines7a,7b,7c, and7dare used for transmission of an electric signal between electrical processing LSI2and optical transceiver101. InFIG. 6, a line for signal transmission is indicated by one straight line. However, the line for signal transmission may be formed of a pair of differential signals (i.e., two lines).

Pins43ato43iof the optical transceiver include a pin (electrical contact) available for outputting an electric signal from an optical reception unit through the electrical contact of the connector to host board1. Further, pins43ato43iof the optical transceiver include a pin that is available for transmitting an electric signal from electrical processing LSI2from the electrical contact of the connector and a pin for outputting information stored in the optical transceiver. Each pin is connected to a corresponding electrical contact of the connector (port11).

An electric signal indicative of the information regarding transmission capacity is transmitted from optical transceiver111through control signal line9to electrical processing LSI2. Electrical processing LSI2may transmit a signal for controlling an optical transceiver to the optical transceiver connected to port11(connector) through control signal line9or another signal line, which is not shown inFIG. 6.

FIG. 7is a block diagram showing a schematic configuration regarding downstream signal processing of electrical processing LSI2. With reference toFIG. 7, electrical processing LSI2includes a data transfer unit21, a media access control (MAC)22, a reconciliation sublayer (RS)23, a physical coding sublayers (PCSs)24a,24b,24c, and24d, physical medium attachments (PMAs)25a,25b,25c, and25d, a multi-lane distribution controller26, and a lane number determination unit27.

Data transfer unit21, MAC22, RS23, PCSs24ato24d, and PMAs25a,25b,25c, and25dcommunicate externally and implement a communication unit for communication with the optical transceiver through the connector. As shown inFIG. 6, electrical processing LSI2is electrically connected to the optical transceiver through the electrical contact of the connector (port11).

Data transfer unit21performs processing such as processing of relaying a MAC frame, concentration processing of bundling traffic from MACs, or link aggregation for connection with a high-order device over a plurality of lines. MAC22provides a logical link identifier (LLID) indicative of a frame destination to an Ethernet (registered trademark) MAC frame and converts the MAC frame into a PON MAC frame. Then, MAC22stores data per LLID in a physical or logical data buffer provided per LLID.

Multi-lane distribution controller26instructs RS23to use which lane to transmit data block read amount from data buffer addressed to each LLID and a read data block, using information indicating to which lane the destination of each LLID is connected and lane information of the optical transceiver connected to the port, which are managed by a multi-point MAC control (MPMC) sublayer.

RS23reads data blocks from data buffer addressed to each LLID of MAC22in units of specific data length or in integral multiples thereof in accordance with the instruction of the multi-lane distribution controller, and provides an LLID indicative of a data destination and a sequence number indicative of a data configuration order. RS23divides the data blocks to transmission buffers provided per lane. “In units of specific data length” may be in units of code length of forward error correction (FEC) processed by PCS.

Each of PCSs24ato24dreads a data block from a transmission buffer provided per lane, adjusts a gap between MAC frames, performs 64B/66B encoding, and performs FEC encoding. Further, each of PMAs25ato25dperforms parallel-serial conversion for interface with the optical transceiver.

On the other hand, received data of a plurality of lanes which has been transmitted from the optical transceiver is subjected to processing such as 64B/66B decoding, FEC decoding, and descrambling in a corresponding PCS of PCSs24ato24d, and is temporarily stored in a reception buffer (not shown). After the receipt of data blocks, in correspondence with an LLID (indicating from which ONU the data is transmitted) provided to the data block and the sequence number indicative of the data configuration order provided to the data block, MAC22divides the data blocks to the respective physical or logical data buffers addressed to the LLIDs, provided per LLID, and converts a PON MAC frame into an Ethernet (registered trademark) MAC frame. Data transfer unit21acquires data from the data buffers in the order of sequence numbers indicative of a data configuration order, and performs processing such as processing of relaying MAC frame, concentration processing of bundling traffic from MACs, and link aggregation for connection with a high-order device over a plurality of lines.

Multi-lane distribution controller26and lane number determination unit27implement a management unit on host board1. The management unit receives lane information regarding an available lane of optical transceiver111from a controller41of optical transceiver111through the connector. The management unit specifies an electrical contact of a connector corresponding to the available lane, that is, an available electrical contact of the connector. Consequently, the transmission capacity can be incrementally upgraded.

Specifically, lane number determination unit27reads lane information regarding an available lane of optical transceiver111from controller41of optical transceiver111. Lane number determination unit27determines the number of lanes of optical transceiver111based on the read information. When the lane information includes information on a wavelength used by each lane, lane number determination unit27can also have the function of determining the wavelength of each lane.

One or more corresponding PMAs of PMAs25ato25dtransmit data to optical transceiver111. As shown inFIG. 6, each of electrical contacts4ato4dand electrical contacts6ato6dof the connector is allocated to a corresponding one lane. Specifying an available lane specifies an available electrical contact associated with the lane from the electrical contacts. Consequently, a circuit block configuring a communication unit of electrical processing LSI2can communicate information (i.e., information transmitted from host board1by a downstream signal) with the optical transceiver via the specified electrical contact.

Optical transceiver111includes controller41. Controller41monitors and controls optical transceiver111. Further, controller41stores lane information regarding a lane and transmits the lane information to host board1. A memory for storing lane information may be provided separately from controller41in optical transceiver111.

In an optical transceiver described below, similarly, controller41notifies host board1of lane information regarding a lane. The lane information can be defined as information for specifying an electrical contact (a pin of the optical transceiver) for transmitting an electric signal output from the optical transceiver to host board1(electrical processing LSI2). Further, the lane information can be defined as information for specifying an electrical contact of a connector for transmitting an electric signal output from host board1(electrical processing LSI2) to the optical transceiver. Further, the lane information can include information for specifying an optical transmission unit for transmitting an optical signal or an optical reception unit for receiving an optical signal. This is because the optical transmission unit or the optical reception unit is associated with a lane.

FIG. 8shows a first example of the lane information. With reference toFIG. 8, the lane information may include lane support information. The support information is information indicating the presence or absence of transmission and the presence or absence of reception for each of four lanes (Lane 1, Lane 2, Lane 3, Lane 4).

FIG. 9shows a second example of the lane information. With reference toFIG. 9, the lane information may include lane wavelength information. The wavelength information indicates a wavelength for each lane of an optical signal transmitted and a wavelength for each lane of an optical signal received.

Optical transceiver111may have one of the lane support information shown inFIG. 8and the lane wavelength information shown inFIG. 9. Alternatively, optical transceiver111may have both the lane support information and the lane wavelength information.

FIG. 10shows an example configuration of the lane information stored in optical transceiver111. With reference toFIG. 10, the lane information is, for example, information stored in a register of controller41. For example, a transmitter lane and a receiver lane are each formed of 4 bits. Each bit indicates a number of a lane (Lane 0, Lane 1, Lane 2, Lane 3) and the presence or absence of implementation of the lane. The transmitter wavelength and the receiver wavelength are each formed of 2 bits×4=8 bits. Two bits of each wavelength indicates a number of a lane and a wavelength of an optical signal in the lane.

FIG. 11shows a third example of the lane information. With reference toFIG. 11, controller41stores information on a transmission capacity supported by an optical transceiver.FIG. 11shows, as an example, a transmission capacity (25 G, 50 G, or 100 G) in transmission and a transmission capacity (25 G, 50 G, or 100 G) in reception. Electrical processing LSI2may have information for associating a transmission capacity and the number of lanes to each other, and information regarding a wavelength of an optical signal (transmission and reception) of each lane. Electrical processing LSI2may acquire support information on a transmission capacity from controller41and expand the support information to the lane information.

The format of the information regarding a lane is not limited as shown inFIGS. 8 to 11. Returning back toFIG. 6, it suffices that host board1has electrical contact8for receiving information regarding a lane from the optical transceiver. For example, the information regarding the number of lanes may be assigned to pins (not shown) of the optical transceiver in contact with electrical contact8. Electrical processing LSI2receives a signal output from electrical contact8through control signal line9. This allows electrical processing LSI2to acquire the information regarding the number of lanes from the optical transceiver.

FIG. 12is a flowchart showing a flow of multi-lane distribution control by electrical processing LSI2shown inFIG. 7. With reference toFIGS. 7 and 12, in step S1, an optical transceiver (e.g., optical transceiver111) is connected to port11of host board1. Electrical processing LSI2receives a signal from a specific pin (e.g., MOD_ABS) of the pins assigned to the optical transceiver and detects plug-in to host board1by the optical transceiver. For example, plug-in to host board1by the optical transceiver may be detected by the state of this signal changing from high to low.

In step S2, electrical processing LSI2reads lane information from optical transceiver111.

In step S3, lane number determination unit27of electrical processing LSI2determines lane information. In step S4, lane number determination unit27determines the number of independent channels based on the number of lanes included in the lane information and the wavelength information (seeFIG. 10).

For example, if the number of lanes is four and the wavelength information in each lane is (λ0, 0, 0, 0), lane number determination unit27determines that the number of independent channels of 25 Gbps is four. Note that “λ0” correctively represents wavelengths λt0 and λr0 (the same applies to λ1, λ2, λ3 described below).

For example, if the number of lanes is four and the wavelength information in each lane is (λ0, λ1, λ2, λ3), lane number determination unit27determines that the number of independent channels of 100 Gbps is one.

For example, if the number of lanes is four and the wavelength information in each lane is (λ0, λ1, λ0, λ1), lane number determination unit27determines that the number of independent channels of 50 Gbps is two.

For example, if the number of lanes is two and the wavelength information in each lane is (λ0, λ1), lane number determination unit27determines that the number of independent channels of 50 Gbps is one.

In step S5, multi-lane distribution controller26expands the determination of the number of independent channels to multi-lane distribution control. Multi-lane distribution controller26distributes and passes transmission data to a lane configuring an independent channel.

FIG. 13shows a stage (Day 1) at which the transmission capacity is 25 Gbps in the scenario for implementing incremental upgrade of transmission capacity according to Embodiment 1. With reference toFIG. 13, optical transceiver101(25 Gbps, wavelength λ1) is connected to port11of host board1. At this stage, the number of lanes is one, and the number of independent channels is one.

FIG. 14shows a stage (Day 2) at which the transmission capacity has been expanded to 50 Gbps from the stage shown inFIG. 13. With reference toFIG. 14, two-wavelength-integrated optical transceiver103(25 Gbps, wavelengths λ1, λ2) is connected to port11. At this stage, the number of lanes is two, and the number of independent channels of 50 Gbps is one.

FIG. 15shows a stage (Day 3) at which the transmission capacity is 100 Gbps in the scenario for implementing incremental upgrade of transmission capacity according to Embodiment 1. With reference toFIG. 15, a four-wavelength-integrated optical transceiver111(25 Gbps, wavelengths λ1, λ2, λ3, λ4) is connected to port11of host board1. At this stage, the number of lanes is four, and the number of independent channels is one. A shift to the stage of Day 3 can be made following Day 1, and subsequently following Day 2.

FIG. 16shows a stage (Day 3′) at which optical network units having a transmission capacity of 25 Gbps have been increased from the stage shown inFIG. 13. With reference toFIG. 16, a band requested by a user is 25 Gbps. Optical transceiver121(25 Gbps, wavelength λ1×4) is connected to port11. At this stage, the number of lanes is four, and the number of independent channels is four.

Normally, the integration of an electric circuit (LSI) is more advanced than the integration of an optical transceiver. In the scenario shown inFIGS. 13 to 16, host board1highly integrated is introduced from the first day (Day 1). Host board1has a configuration with high port density, which takes into account the stage of Day 3 from the beginning. The degree of integration of the optical transceiver connectable with port11is increased with higher integration of an optical transceiver. In the scenario shown inFIGS. 13 to 16, when a required transmission capacity (user requested band) is low, the power consumption or cost of an optical transceiver can be reduced. The optical transceiver connected to port11is exchanged with an optical transceiver having a higher degree of integration, thus increasing transmission capacity. This allows incremental upgrade of transmission capacity without the need for exchanging a host board. Further, according to the present embodiment, an empty port in Day 1 does not need to be mounted in a host board in advance.

FIG. 17shows a schematic configuration of an optical transceiver applicable to Embodiment 1.FIG. 17shows an optical transceiver111aas an example. Optical transceiver111aincludes controller41, electrical interface43, a clock data recovery (CDR) IC44, a power supply IC45, a temperature control IC46, a transmission module50, and a reception module60. Controller41monitors and controls optical transceiver111a. Further, controller41stores lane information regarding a lane and transmits the lane information to host board1. A memory for storing the lane information may be provided separately from controller41in optical transceiver111a.

Electrical interface43receives and outputs an electric signal from and to electrical processing LSI2. Transmission module50outputs data from clock data recovery IC44in the form of an optical signal. Transmission module50may include a Peltier device48. Temperature control IC46sends a control signal to Peltier device48to control the temperature of transmission module50.

Reception module60receives an optical signal and converts the optical signal into an electric signal. The electric signal from reception module60is transmitted to clock data recovery IC44.

Clock data recovery IC44is not limited to one built in an optical transceiver and may be provided between the optical transceiver and electrical processing LSI2in host board1. Alternatively, clock data recovery IC44may be built in electrical processing LSI2.

Further, a clock data recovery IC on the transmission side and a clock data recovery IC on the reception side may be provided separately. The clock data recovery ICs may be provided between the optical transceiver and the host board or in the electrical processing LSI separately from each other.

The following will describe an example schematic configuration of an optical transceiver applicable to the scenario of incremental upgrade of transmission capacity. For easy understanding, the following figures mainly show the portions regarding the transmission and reception of an optical signal. Clock data recovery IC44, power supply IC45, temperature control IC46, and Peltier device48are not shown in the figures described below.

FIGS. 18 to 20show example configurations of a single-core bidirectional optical transceiver.FIG. 18shows an example configuration of an optical transceiver capable of incremental upgrade of transmission capacity. With reference toFIG. 18, optical transceiver101supports a lane of 25 Gbps×1. Optical transceiver101includes controller41, an optical wavelength multiplexer/demultiplexer (MUX/DMUX)42, electrical interface43, an optical transmission unit51, and an optical reception unit61.

Optical wavelength multiplexer/demultiplexer42is optically connected to PON line303. Optical wavelength multiplexer/demultiplexer42is mounted on optical transceiver101to transmit a plurality of optical signals with different wavelengths over PON line303. Specifically, optical wavelength multiplexer/demultiplexer42outputs an optical signal with a wavelength λt1 from optical transmission unit51to PON line303and outputs an optical signal with wavelength λr1 from PON line303to optical reception unit61.

Optical transmission unit51receives an electric signal through electrical interface43and converts the electric signal into an optical signal with wavelength λt1. Optical transmission unit51outputs the optical signal to PON line303through optical wavelength multiplexer/demultiplexer42.

Optical reception unit61receives the optical signal with wavelength λr1 from PON line303through optical wavelength multiplexer/demultiplexer42and converts the optical signal into an electric signal. Optical reception unit61outputs the electric signal to electrical interface43.

FIG. 19shows an example configuration of an optical transceiver capable of incremental upgrade of transmission capacity. As shown inFIG. 19, optical transceiver103supports 25 Gbps×2 lanes. Optical transceiver103can be used for achieving a transmission capacity of 50 Gbps.

Optical transceiver103includes an optical transmission unit52and an optical receiver62in addition to the configuration shown inFIG. 18. Optical transmission unit52receives an electric signal through electrical interface43and converts the electric signal into an optical signal with wavelength λt2. Optical receiver62receives an optical signal with wavelength λr2 from PON line303through optical wavelength multiplexer/demultiplexer42and converts the optical signal into an electric signal.

Optical wavelength multiplexer/demultiplexer42multiplexes an optical signal with wavelength λt1 transmitted from optical transmission unit51and an optical signal with wavelength λt2 transmitted from optical transmission unit52and outputs a wavelength multiplexed signal to PON line303. On the other hand, optical wavelength multiplexer/demultiplexer42receives a wavelength multiplexed signal from PON line303and demultiplexes the wavelength multiplexed signal into two optical signals (wavelengths λr1, λr2).

FIG. 20shows an example configuration of an optical transceiver capable of incremental upgrade of transmission capacity. As shown inFIG. 20, optical transceiver111supports 25 Gbps×4 lanes. Optical transceiver111can be used for achieving a transmission capacity of 100 Gbps.

Optical transceiver111includes optical transmission units53and54and optical reception units63and64, in addition to the configuration shown inFIG. 19. Each of optical transmission units53and54receives an electric signal through electrical interface43. Optical transmission units53and54output an optical signal with wavelength λt3 and an optical signal with wavelength λt4, respectively. Optical reception units63and64receive an optical signal with wavelength λr3 and an optical signal with wavelength λr4, respectively, from PON line303through optical wavelength multiplexer/demultiplexer42. Each of optical reception units63and64converts the received optical signal into an electric signal.

FIGS. 21 to 23show an example configuration of a dual-core optical transceiver. As shown inFIGS. 21 to 23, the optical wavelength multiplexer/demultiplexer is connected to an optical transceiver. With reference toFIGS. 18 and 21, an optical transceiver101adiffers from optical transceiver101in that it includes no optical wavelength multiplexer/demultiplexer. Similarly to optical transceiver101, optical transceiver101acan be used for achieving a transmission capacity of 25 Gbps.

With reference toFIG. 22, an optical transceiver103aincludes transmission module50and reception module60. Similarly to optical transceiver103, optical transceiver103acan be used for achieving a transmission capacity of 50 Gbps.

Transmission module50includes optical transmission units51and52and an optical wavelength multiplexer (MUX)55. Optical wavelength multiplexer55multiplexes optical signals from optical transmission units51and52to generate a wavelength multiplexed signal. The wavelength multiplexed signal is output to PON line303through optical wavelength multiplexer/demultiplexer31.

Reception module60includes optical reception units61and62and an optical wavelength demultiplexer (DMUX)65. Wavelength demultiplexer65receives a wavelength multiplexed signal from PON line303and demultiplexes the wavelength multiplexed signal into two optical signals (wavelengths λr1, λr2). Optical reception units61and62receive an optical signal with wavelength λr1 and an optical signal with wavelength λr2, respectively.

With reference toFIG. 23, optical transceiver111aincludes transmission module50and reception module60. Similarly to optical transceiver111, optical transceiver111acan be used for achieving a transmission capacity of 100 Gbps.

Optical transceiver111adiffers from optical transceiver103ain the configurations of transmission module50and reception module60. Transmission module50includes optical transmission units51,52,53, and54, and reception module60includes optical reception units61,62,63, and64. The following will not repeat description of optical transmission units51,52,53, and54and optical reception units61,62,63, and64.

Optical wavelength multiplexer55multiplexes optical signals from optical transmission units51,52,53, and54to generate a wavelength multiplexed signal. Wavelength demultiplexer65receives a wavelength multiplexed signal from PON line303and demultiplexes the wavelength multiplexed signal into four optical signals (wavelengths λr1, λr2, λr3, λr4).

As described above, the wavelength of an optical signal received by each optical reception unit is determined in advance. For example, when optical transceiver101shown inFIG. 18receives an optical signal subjected to wavelength multiplexing, optical wavelength multiplexer/demultiplexer42outputs only an optical signal with wavelength λr1. In this manner, the optical transceiver according to Embodiment 1 converts an optical signal with a wavelength associated with a transmission capacity supported into an electric signal and outputs the electric signal to host board1. The optical transceiver does not output optical signals with the other wavelengths to host board1. In other words, the optical transceiver ignores optical signals with wavelengths other than reception objects.

In Embodiment 1, the shape of the optical transceiver is standardized to allow an optical transceiver for 25 G, an optical transceiver for 50 G, and an optical transceiver for 100 G to be connected to a connector on the host board1side. Exchanging an optical transceiver connected to a connector can allow incremental transmission capacity expansion.

FIG. 24shows another example configuration of an optical transceiver applicable to Embodiment 1. As shown inFIG. 24, optical transceiver121includes four optical wavelength multiplexer/demultiplexers42. Each of optical transmission units51to54transmits an optical signal with wavelength λt1. Each of optical reception units61to64receives an optical signal with wavelength λr1. Each optical wavelength multiplexer/demultiplexer42is connected to one optical transmission unit and one optical reception unit. Optical transceiver121supports 25 Gbps×4 lanes.

FIG. 25shows another example configuration of an optical transceiver applicable to Embodiment 1. As shown inFIG. 25, optical transceiver104includes transmission modules50and50A and reception modules60and60A. Transmission module50A and reception module60A have the same configurations as those of transmission module50and reception module60. Thus, detailed descriptions of the configurations of transmission module50A and reception module60A will not be repeated. Optical transceiver121supports 25 Gbps×4 lanes.

Optical transceiver104is optically connected to two optical wavelength multiplexer/demultiplexers31. Each optical wavelength multiplexer/demultiplexer31is connected to PON line303. In the configuration shown inFIG. 25, the number of independent channels of 50 Gbps is two. Each of two PON lines303can achieve a transmission capacity of 50 Gbps.

FIG. 26shows another example configuration of an optical transceiver applicable to Embodiment 1. As shown inFIG. 26, optical transceiver112has the same configuration as that of optical transceiver111(seeFIG. 20). Controller41outputs an enable signal and a disable signal to each of optical transmission units51to54and optical reception units61to64. Controller41may receive a signal externally from optical transceiver112through electrical interface43and output an enable signal and a disable signal in response to the signal. Each of optical transmission units51to54and optical reception units61to64is activated by an enable signal, whereas it is deactivated by a disable signal.

FIG. 27shows a configuration for supporting 25 Gbps by optical transceiver112shown inFIG. 26. As shown inFIG. 27, controller41transmits an enable signal to optical transmission unit51and optical reception unit61and transmits a disable signal to another optical transmission unit and another optical reception unit. Activation of optical transmission unit51and optical reception unit61achieves 25 Gbps×1 lane.

FIG. 28shows a configuration for supporting 50 Gbps by optical transceiver112shown inFIG. 26. As shown inFIG. 28, controller41transmits an enable signal to optical transmission units51and52and optical reception units61and62and transmits a disable signal to another optical transmission unit and another optical reception unit. Activation of optical transmission units51and52and optical reception units61and62can achieve 25 Gbps×2 lanes.

FIG. 29shows a configuration for supporting 100 Gbps by optical transceiver112shown inFIG. 26. As shown inFIG. 29, controller41transmits an enable signal to optical transmission units51,52,53, and54and optical reception units61,62,63, and64. Activation of optical transmission units51to54and optical reception units61to64can achieve 25 Gbps×4 lanes.

FIG. 30shows another example configuration of an optical transceiver applicable to Embodiment 1. As shown inFIG. 30, optical transceiver122has the same configuration as that of optical transceiver121(seeFIG. 21). Controller41transmits an enable signal or a disable signal to each of optical transmission units51to54and optical reception units61to64. In the example shown inFIG. 30, controller41transmits an enable signal to optical transmission unit51and optical reception unit61and transmits a disable signal to another optical transmission unit and another optical reception unit. Optical transmission unit51and optical reception unit61are activated. Thus, optical transceiver121is equivalent to optical transceiver101with one channel (wavelength λ1) of 25 Gbps.

FIG. 31shows an example configuration for supporting the transmission of 25 Gbps×4 channels by optical transceiver122shown inFIG. 30. With reference toFIG. 31, controller41transmits an enable signal to optical transmission units51to54and optical reception units61to64. This activates optical transmission units51to54and optical reception units61to64.

In the configurations shown inFIGS. 26 to 31, controller41sends an enable/disable signal in optical transceivers112and122. However, the host board1side (e.g., electrical processing LSI2or another control block on the host board) may directly supply an enable/disable signal to the optical transmission units and the optical reception units of optical transceivers112and122through a port (connector), not through controller41.

FIG. 32shows another example of a scenario of incremental upgrade of transmission capacity. With reference toFIG. 32, at the first stage, optical transceiver121is connected to port11. Further, optical wavelength multiplexer/demultiplexers31a,31b,31c, and31dare optically connected to optical transceiver121. This enables the transmission of an optical signal by 25 Gbps×4 channels.

At the second stage, optical transceiver121ais connected to port12and is optically connected to optical wavelength multiplexer/demultiplexers31a,31b,31c, and31d. Optical transceiver121ahas the same configuration as that of optical transceiver121except for that the wavelength of an optical signal is λ2 (λt2, λr2). Optical wavelength multiplexer/demultiplexers31a,31b,31c, and31dsubject optical signals from optical transceivers121and121ato wavelength multiplexing and demultiplex a wavelength multiplexed signal from a PON line (not shown) into an optical signal with wavelength λr1 and an optical signal with wavelength λr2. This enables the transmission of optical signals by 50 Gbps×4 channels.

FIG. 33shows a configuration for upgrading a transmission capacity from the configuration shown inFIG. 32. The configuration shown inFIG. 33differs from the configuration shown inFIG. 29in that optical transceivers121band121care connected to ports13and port14, respectively. The wavelength of optical transceiver121bis λ3 (λt3, λr3), and the wavelength of optical transceiver121cis λ4 (λt4, λr4).

Optical wavelength multiplexer/demultiplexers31a,31b,31c, and31dsubject optical signals from optical transceivers121,121a,121b, and121cto wavelength multiplexing and demultiplex a wavelength multiplexed signal from a PON line (not shown) into an optical signal with wavelength λr1, an optical signal with wavelength λr2, an optical signal with wavelength λr3, and an optical signal with wavelength λr4. This enables transmission of optical signals by 100 Gbps×4 channels. As shown inFIGS. 32 and 33, the embodiment of the present invention enables a transmission capacity of Day 3×4 by four ports on the host board.

The overall configuration of an optical communication system according to Embodiment 2 is identical to the configuration shown inFIG. 1. Specifically, a previous generation system and a new generation system coexist in Embodiment 2. In this embodiment, “previous generation system” refers to a system with low transmission capacity, and “new generation system” refers to a system with high transmission capacity.

In the description of Embodiment 2, the term “Day 0” refers to a stage before the transmission capacity is expanded, that is, a previous generation. In one embodiment, the transmission capacity in Day 0 is 10 Gbps.

Since a previous generation system with low transmission capacity has become widespread, a system in which a previous generation system and a new generation system coexist may be requested. For example, when a system of 10 G has been introduced, a new generation (25 G, 50 G, 100 G) system can preferably accommodate an existing system (10 G). Embodiment 2 provides a system that can coexist with a previous generation system.

FIG. 34shows a stage (Day 0) at which the transmission capacity is 10 Gbps. InFIG. 34, an optical transceiver131(wavelength λ0) for 10 Gbps, an electrical processing LSI2A, and a concentration LSI3are mounted on a host board1A.

FIG. 35shows a stage (Day 1) at which a system of 10 Gbps and a system of 25 Gbps coexist in one scenario of transmission capacity expansion. In comparison betweenFIGS. 34 and 35, at the stage of Day 1, optical network unit302of 25 Gbps is introduced into a system in addition to optical network unit302of 10 Gbps. Thus, host board1A is exchanged with a host board1B. Optical transceiver141, electrical processing LSIs2and2A, and concentration LSI3are mounted on host board1B.

Optical transceiver141can support both of transmission capacities of 10 Gbps (wavelength λ0) and 25 Gbps (wavelength λ1). Electrical processing LSI2A communicates information with host board1B externally, similarly to electrical processing LSI2. Electrical processing LSI2A is an LSI for transmission processing at 10 Gbps. Electrical processing LSI2A differs from electrical processing LSI2in this respect.

FIG. 36shows a stage (Day 2) at which a system of 10 Gbps, a system of 25 Gbps, and a system of 50 Gbps coexist in one scenario of transmission capacity expansion. In comparison with the configuration shown inFIG. 35, inFIG. 36, an optical transceiver151is mounted on host board1B in place of optical transceiver141. Optical transceiver151is an optical transceiver with 10 Gbps×1 wavelength (wavelength λ0) and 25 Gbps×2 wavelengths (λ1, λ2).

FIG. 37shows a stage (Day 3) at which systems of 10 Gbps, 25 Gbps, 50 Gbps, and 100 Gbps coexist in one scenario of transmission capacity expansion. In comparison with the configuration shown inFIG. 36, inFIG. 37, an optical transceiver161is mounted on host board1B in place of optical transceiver151. Optical transceiver161is an optical transceiver with 10 Gbps×1 wavelength (wavelength λ0) and 25 Gbps×4 wavelengths (λ1, λ2, λ3, λ4).

FIG. 38shows one form of host board at the stage of Day 1.FIG. 39shows one form of host board at the stage of Day 3. As shown inFIGS. 38 and 39, host board1B is configured to accommodate one previous generation (10 Gbps) lane and four new generation lanes. Electrical processing LSI2A executes processing for transmission of 10 Gbps. Electrical processing LSI2A executes processing for transmission in a plurality of lanes (N lanes) of 25 Gbps.

Optical transceivers141and161support a previous generation transmission capacity (e.g., 10 Gbps). Optical transceiver141implements one lane for new generation in addition to one lane for previous generation. Optical transceiver161implements four lanes for new generation in addition to one lane for previous generation. Optical transceiver141and optical transceiver161have the same form. Consequently, optical transceiver141is easily exchangeable with optical transceiver161.

FIG. 40is a block diagram showing a schematic configuration for controlling transmission capacity in Embodiment 2. With reference toFIG. 40, an optical transceiver monitoring control block20on host board1B reads information on transmission capacity which is supported by an optical transceiver from controller41of the optical transceiver (e.g., optical transceiver161). For example, optical transceiver monitoring control block20determines whether the optical transceiver corresponds to any of one lane, two lanes, and four lanes from the information from controller41of the optical transceiver. Further, optical transceiver monitoring control block20determines whether the optical transceiver corresponds to a previous generation (e.g., 10 Gbps) system from the information from controller41of the optical transceiver. Host board1B controls a data flow in accordance with the rate (the number of lanes) at which a signal is received from and output to optical transceiver161and the presence or absence of a previous generation system, based on the information read by optical transceiver monitoring control block20.

FIG. 41schematically shows a configuration regarding the electric connection between an optical transceiver, a port, and an electrical processing LSI in Embodiment 2.FIG. 41shows optical transceiver161. As in the configuration shown inFIG. 6, in Embodiment 2, port11is implemented by a connector. In Embodiment 2, the connector has electrical contacts4eand6ein addition to electrical contacts4a,4b,4c,4d,6a,6b,6c,6d, and8shown inFIG. 6. Electrical contacts4eand6eare connected to high-rate signal lines5eand7e, respectively. In Embodiment 2, high-rate signal lines5a,5b,5c,5d, and5eform one pair, and high-rate signal lines7a,7b,7c,7d, and7eform another pair.

Optical transceiver161includes electrical interface43. Electrical interface43has pins43jand43kin addition to pins43ato43i. With optical transceiver161connected to the connector (port11), pins43jand43kare electrically connected to electrical contacts4eand6e, respectively. The other pins are similar to the corresponding pins of electrical interface43according to Embodiment 1, description of which will not be repeated.

FIG. 42shows an example configuration of the optical transceiver according to Embodiment 2. As shown inFIG. 42, optical transceiver141supports lanes of 10 Gbps×1 and 25 Gbps×1. Optical transceiver141includes an optical transmission unit56and an optical reception unit66in addition to the configuration of optical transceiver101shown inFIG. 18.

Optical transmission unit56receives an electric signal through electrical interface43and converts the electric signal into an optical signal with wavelength λt0. Optical transmission unit56outputs the optical signal to PON line303through optical wavelength multiplexer/demultiplexer42. Optical reception unit66receives an optical signal with wavelength λr0 from PON line303through optical wavelength multiplexer/demultiplexer42and converts the optical signal into an electric signal. Optical reception unit66outputs the electric signal to electrical interface43. Detailed descriptions of optical transmission unit56and optical reception unit66will not be repeated.

FIG. 43shows another example configuration of the optical transceiver according to Embodiment 2. As shown inFIG. 43, optical transceiver151supports lanes of 10 Gbps×1 and 25 Gbps×2. Optical transceiver151includes optical transmission unit56and optical reception unit66in addition to the configuration of optical transceiver103shown inFIG. 19.

FIG. 44shows still another example configuration of the optical transceiver according to Embodiment 2. As shown inFIG. 44, optical transceiver161supports lanes of 10 Gbps×1 and 25 Gbps×4. Optical transceiver161includes optical transmission unit56and optical reception unit66in addition to the configuration of optical transceiver103shown inFIG. 19.

FIG. 45shows another example configuration of the optical transceiver in which an existing transmission capacity and a large capacity can coexist. As shown inFIG. 45, an optical transceiver141A supports lanes of 10 Gbps×1 and 25 Gbps×1. In comparison with the configuration of optical transceiver141shown inFIG. 42, optical transceiver141A includes an optical reception unit61A in place of optical reception units61and66. Optical reception unit61A receives an optical signal obtained by time division multiplexing of wavelength λr0 and wavelength λr1 through optical wavelength multiplexer/demultiplexer42from PON line303and converts the optical signal into an electric signal. Optical reception unit61A divides the electric signals to the lane for 10 Gbps and the lane for 25 Gbps and outputs the electric signals to electrical interface43. Detailed description of optical reception unit61A will not be repeated.

FIG. 46shows another example configuration of the optical transceiver in which an existing transmission capacity and a large capacity can coexist. As shown inFIG. 46, optical transceiver151A supports lanes of 10 Gbps×1 and 25 Gbps×2. In comparison with the configuration of optical transceiver151shown inFIG. 43, optical transceiver151A includes optical reception unit61A in place of optical reception units61and66.

FIG. 47shows still another example configuration of the optical transceiver in which an existing transmission capacity and a large capacity can coexist. As shown inFIG. 47, optical transceiver161A supports lanes of 10 Gbps×1 and 25 Gbps×4. In comparison with the configuration of optical transceiver161shown inFIG. 44, optical transceiver161A includes optical reception unit61A in place of optical reception units61and66.

FIG. 48is a diagram for illustrating the reception of an optical signal by the optical transceiver shown inFIGS. 42 to 44. As shown inFIG. 48, an optical signal with wavelength λr0 and an optical signal with wavelength λr1 coexist in PON line303by wavelength division multiplexing (WDM). Thus, optical wavelength multiplexer/demultiplexer42separates an optical signal with wavelength λr0 and an optical signal with wavelength λr1 from each other.

FIG. 49is a diagram for illustrating the reception of an optical signal by the optical transceiver shown inFIGS. 45 to 47. As shown inFIG. 49, an optical signal with wavelength λr0 and an optical signal with wavelength λr1 coexist in PON line303by time division multiplexing (TDM). Optical wavelength multiplexer/demultiplexer42does not separate an optical signal with wavelength λr0 and an optical signal with wavelength λr1 from each other. Thus, optical reception unit61A receives time division multiplexed signals (an optical signal with wavelength λr0 and an optical signal with wavelength λr1). The optical transceiver shown inFIGS. 42 to 47transmits an optical signal by WDM.

FIG. 50is a block diagram showing a schematic configuration regarding downstream signal processing of electrical processing LSI according to Embodiment 2. With reference toFIG. 50, a host board1B additionally has a configuration for downstream data transmission for 10 Gbps, in addition to the configuration shown inFIG. 7. Specifically, the configuration for 10 Gbps includes a MAC22A, an RS23A, a PCS24, and a PMA25. Further, a 100 G data client block21A divides data lanes as a data transfer unit in accordance with a transmission capacity requested by a user. The lane for 10 Gbps is defined as “Lane 0” below.

100 G data client block21A, MACs22and22A, RSs23and23A, and PCS24and24ato24d, and PMAs25and25ato25dimplement a communication unit that communicates externally and communicates with an optical transceiver through a connector. Multi-lane distribution controller26and lane number determination unit27implement a management unit on host board1B. The management unit implements optical transceiver monitoring control block20shown inFIG. 40. The management unit receives lane information regarding an available lane of an optical transceiver from controller41of the optical transceiver (seeFIG. 40) through the connector. The management unit specifies an electrical contact of a connector corresponding to the available lane, that is, an available electrical contact of the connector.

FIG. 51shows a first example of the lane information according to Embodiment 2.FIG. 52shows a second example of the lane information according to Embodiment 2.FIG. 53shows a third example of the lane information according to Embodiment 2. In Embodiment 2, the information on Lane 0 is added to the lane information shown inFIGS. 8, 9, and 11. Thus, a plurality of lanes include a first lane (Lane 0) for a first transmission capacity (10 G) of an optical transceiver, an optical transmitter, and an optical receiver, and a second lane (Lane 1, Lane 2, Lane 3, Lane 4) for a second transmission capacity (25 G, 50 G, 100 G) of an optical transceiver, an optical transmitter, and an optical receiver, which differs from the first transmission capacity. This allows coexistence of a previous generation system having a low transmission capacity and a new regeneration system having a high transmission capacity.

Since an optical network unit is installed per service subscriber, a system includes an optical network unit having a different transmission capacity. In Embodiment 2, the optical line terminal allows coexistence of a previous generation system and a new generation system only by exchange of optical transceivers. Further, in Embodiment 2, a new generation system can incrementally upgrade transmission capacity without exchanging host boards. Consequently, Embodiment 2 can achieve high scalability while preventing the configuration of the optical line terminal from becoming complicated.

All the embodiments of the present invention can exchange an optical transceiver connected to a host board to incrementally change transmission capacity. Note that all the embodiments described above show a scenario of expanding transmission capacity. In all the embodiments of the present invention, however, the scenario of changing transmission capacity can include downgrading of transmission capacity.

Further, all the embodiments of the present invention can implement an optical receiver that notifies a host board of lane information by a wavelength demultiplexing unit, at least one optical receiver, an electrical interface, and a controller (communication unit) of an optical transceiver. Similarly, all the embodiments of the present invention can implement an optical transmitter that notifies a host board of lane information by a wavelength multiplexing unit, at least one optical transmission unit, an electrical interface, and a controller (communication unit) of an optical transceiver.

Each embodiment above has described an example of 25 G×4. All the embodiments of the present invention can also support a transmission capacity of 40 G (10 G×4), incrementally upgrade transmission capacity from 10 G to 40 G, and support coexistence of a previous generation (10 G) and a new generation (expansion from 10 G to 40 G).

The embodiments disclosed herein should be considered illustrative in every respect, not limitative. The scope of the present invention is defined not by the above-described embodiments but by the claims. It is intended that the scope of the present invention includes any modification within the scope and meaning equivalent to the scope of the claims.

REFERENCE SIGNS LIST