Interface board and optical transmission equipment

A circuit capable of processing signals of different signal types is provided for identifying the signal type by the signal type setting from an administrator or by the implementation of the optical module, thereby selecting a signal processor to be used. An OTN frame standardized by ITU is used in a fixed manner independent of the signal type to be accommodated, while a corresponding SDH/SONET frame standardized by ITU is used for signal accommodation.

CLAIM OF PRIORITY

The present application claims priority from Japanese patent application serial no. 2007-064341, filed on Mar. 14, 2007, the content of which is hereby incorporated by reference into this application.

BACKGROUND OF THE INVENTION

The present invention relates to an interface board and optical transmission equipment that multiplex plural optical signals received from plural lines to transmit to a backbone network, as well as demultiplex a multiplexed optical signal received from the backbone network into individual optical signals to transmit to individual lines.

With a recent increase of traffic volume due to the growing number of broadband Internet access lines, there has been a demand to provide high-speed high-capacity networks. As a method to realize this, optical network equipment using Wavelength Division Multiplexing (WDM) technology are widely used. WDM is a technology for multiplexing optical signals of different wavelengths to a single optical fiber, able to easily realize high-capacity communication by addition of the number of wavelengths to be multiplexed without installation of new optical fibers. In recent years, networks having more flexible and various functions are desired, such as dropping and adding of any wavelengths at intermediate nodes, in addition to providing high-capacity communication. Such network transmission equipment is called Optical Add Drop Multiplexer (OADM).

Further, in recent years, signals connected to a network have been diversified according to their applications. Such signals are exemplified by Ethernet standardized by IEEE802.3, and Synchronous Digital Hierarchy/Synchronous Optical Network (SDH/SONET) standardized by ITU-T G.707 and ANSI TI.105.FIG. 1is a list of signals to be connected to an optical network. As shown inFIG. 1, there are many types of signals to be connected to an optical network, such as SDH/SONET, GbE, 10 GbE, and Fiber Channel. Also, the transmission speeds of these signal types widely vary from 50 Mbps (bit per second) to 40 Gbps.

As described above, the optical network handles many signal types. Adoption of a different monitoring control method for each signal only makes maintenance complicated. For this reason, there has been a demand for providing a network management method independent of the signal type. A typical method for meeting such a demand is a network monitoring using an Optical Transport Network (OTN) frame standardized by ITU-T G. 709. Optical Channel (Och) frame of OTN can be mapped independent of the signal type, allowing an integrated monitoring control of the whole network. In the method using an OTN frame, fault management is possible in the OTN section by accommodating a signal to the OTN frame, adding an overhead for the OTN frame which is different from the accommodation signal, and monitoring the overhead of the OTN frame. Monitoring is also possible to determine the network section in which a failure occurs, the network between transmission equipment items or the network section of an optical signal to be accommodated. Further, long distance transmission is possible by adopting Forward Error Correction (FEC) codes.

Examples of references are as follows:

1. ITU-T G.709 Interface for the optical transport network (OTN)

5. IEEE standard 802.3 Information Technology—Telecommunications and information exchange between systems—Local and metropolitan area networks—Specific requirements—Carrier sense multiple access with collision detection (CSMA/CD) access method and physical layer specifications

6. IEEE standard 802.3ae Information technology—Telecommunications and information exchange between systems—Local and metropolitan area networks—Specific requirements—Part 3: Carrier sense multiple access with collision detection (CSMA/CD) access method and physical layer specifications—Media Access Control (MAC) Parameters, Physical Layer and Management Parameters for 10 Gb/s Operation

There are three transmission speeds defined in OTN: OTU (Optical Channel Transport Unit)-1 for 2.5 Gbps, OTU-2 for 10 Gbps, and OTU-3 for 40 Gbps. However, the low-speed signals with a transmission speed of less than 2.5 Gbps have not been standardized yet.

Meanwhile, because adoption of the OTN optical transmission enables integrated management of a network, mapping to the standardized OTN frame even with the transmission speed of less than 2.5 Gbps is also efficient in terms of network management. Thus, there has been adopted methods of mapping the low-speed signals with transmission speed of less than 2.5 Gbps into OTN frames originally standardized by equipment vendors. In the methods, plural signals are multiplexed in order to apply the transmission speed of less than 2.5 Gbps to the OTN frame standardized by ITU-T G. 709. Conventionally, multiplexing is realized by terminating information called a pointer (PTR) that indicates the frame position in which the first position of the virtual container is multiplexed, in order to map the input signals to the OTN frame. This makes it difficult to connect between transmission equipment items of different equipment vendors due to adoption of the vendor specific OTN frames.

FIG. 1shows signals of different transmission speeds and frame formats. Transmission equipment includes an interface board to connect such signals to a backbone network. The interface board performs processing at an OTN signal speed corresponding to a signal type to be accommodated. Thus, in order to process plural signals, the interface board is necessary to have plural OTN function units. The OTN function units have different configurations for each signal speed, which limits the amount of hardware to be installed in the interface board. For this reason, multi-rate interface boards supporting a wide range of transmission speeds have not been realized, only allowing supporting signals with a limited range of transmission speeds, such as low-speed signals or high-speed signals.

In order to meet the traffic demand that is expected to further increase in the future, it is necessary to provide optical transmission equipment including a flexible multi-rate interface board capable of accommodating signals of different transmission speeds into the OTN frame.

SUMMARY OF THE INVENTION

The present invention addresses these needs by providing optical transmission equipment including an interface board capable of processing different types of signals. In the optical transmission equipment, the interface board determines a signal that can be accommodated by the signal setting from an administrator or by the implementation of an optical module, and selects the signal process to be used. An OTN frame standardized by ITU is used in a fixed manner independent of the signal type to be accommodated, while a corresponding SDH/SONET frame standardized by ITU is used for signal accommodation. The SDH/SONET frame is configured to have a signal speed equal to or higher than the speed of the signal type to be accommodated. Because the OTN frame is used at a fixed rate, not only low-speed signals but also high-speed signals can be supported, without the need for configuring plural OTN frame function units.

The accommodation signal to be accommodated in the SDH/SONET frame can have a transmission speed equal to or lower than the OTN frame rate. Further, even if plural signals can be multiplexed, no multiplexing takes place, and instead the OTN frame is clock synchronized with the signal to be accommodated. This eliminates the clock difference with the signal to be accommodated which can be perfectly transmitted without being terminated.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 2is a hardware block diagram of an optical network using OTN. Signals shown inFIG. 1are output from client devices1-1to1-n(2000), client devices2-1to2-n(2001), or client devices3-1to3-n(2002). The signal are transferred to Och frames in an interface housing1(2003), an interface housing2(2004), or an interface housing3(2005). The Och frames are multiplexed in a wavelength multiplexing unit2006, a wavelength multiplexing unit2007, or a wavelength multiplexing unit2008. Then, the multiplexed signal is connected to an OTN optical network. The wavelength multiplexing units2006to2008are placed in a ring configuration, but able to provide point-to-point transmission with the client devices parts1to3, respectively. Hereinafter, typical two embodiments will be described with reference to the accompanying drawings.

FIG. 3shows the configuration of a multi-rate interface housing3001capable of accommodating signals of different speeds.FIG. 3shows a typical conventional multi-rate interface board3002for comparison, and a multi-rate interface board1of a first embodiment.

The conventional multi-rate interface board3002includes: an optical module unit3004in which an optical module is installed to receive and process optical signals according to various signal types; plural signal processing units (3005to3008) for individual signal types according to various signals; OTN function units (3009to3012) for accommodating OTN frames of various signal types; signal selectors (3013,3014) for selecting one of the signal processors for signal input/output, according to the signal type to be accommodated; and wavelength converters (3015,3016) for converting to a predetermined optical wavelength for wavelength multiplexing.

The optical module unit3004is installed with an optical transceiver module (hereinafter simply referred to as an optical module), which is called Small Form-factor Pluggable (SFP) or 10 Gigabit Small Form-factor Pluggable (XFP), in order to accommodate optical signals of different speeds.

In the conventional multi-rate interface board3002shown inFIG. 3, an STM-16 signal3003of SDH is connected. The OTN function units (3009to3012) are provided with OTN interface functions each having a fixed rate corresponding to each signal. Here, the STM-16 signal is processed by the signal processor2(3006), followed by the OTN function unit2(3010). The signal selector3013selects the OTN function unit3010in which the signal type STM-16 is accommodated, by a monitoring control signal3021. Upon selection of the OTN function unit3010, the wavelength converter3015converts the signal processed by the OTN function unit3010, to an optical signal of a specific wavelength. Then, the optical signal is transmitted to the wavelength multiplexing unit3017. As described above, the conventional multi-rate interface board3002is necessary to have a separate circuit for each signal to be accommodated, causing a cost increase.

To overcome such a problem, in the multi-rate interface board1, the plural signal processors3005,3006having been provided for the wavelength converter3015, are integrated into one multi-rate signal processing unit3, together with a multiplexer/demultiplexer unit4and an OTN function unit5. InFIG. 3, a monitoring controller7monitors the signal quality of the OTN function unit5and controls the multi-rate interface board1, in response to a control signal3022from an upper controller8such as Operation System (OpS). The OTN function units (3009to3012) transfer signals from a client device3000to Och frames. Reference numeral3018shows a client device. Reference numeral3019shows an OTN optical network.FIG. 4shows the details of the multi-rate interface board1shown inFIG. 3.

InFIG. 4, the multi-rate interface board1includes an optical module2, a multi-rate signal processing unit3, a multiplexer/demultiplexer unit4, an OTN function unit5, a wavelength converter6, a type code acquisition unit11, and a monitoring controller7. The multi-rate interface board1is connected, through the monitoring controller7, to the upper controller8in which an administrator can set an accommodation signal.

The optical module2receives a low-speed signal with plural light types, signal speeds, and frame formats, as an optical signal. The optical module2converts the optical signal to an electrical signal, and transmits to the multi-rate signal processing unit3. On the other hand, the optical module2receives an electrical signal from the multi-rate signal processing unit3, converts the electrical signal to an optical signal, and transmits a low-speed signal. Here, the optical module2can be hot pluggable at will according to the signal type.

The multi-rate signal processing unit3further includes: a signal processing unit10for processing a signal with a signal speed and frame format, according to the appropriate signal speed and frame format determined by a mode setting instruction4004from the monitoring controller7, independently in the multiplexing direction and in the demultiplexing direction; and a bandwidth allocation unit9for mapping a signal to a used bandwidth, as well as demapping the used bandwidth according to a bandwidth allocation instruction4006from the monitoring controller7.

The multiplexer/demultiplexer unit4performs multiplexing/demultiplexing of SDH/SONET frames. The OTN function unit5maps signals from the multiplexer/demultiplexer unit4to OTN frames, and reversely demaps the signals from the OTN frames. Hence, signal monitoring is possible independently in the multiplexing direction and in the demultiplexing direction. The wavelength converter6converts an electrical signal to an optical signal to transmit a high-speed optical signal. On the other hand, the wavelength converter6receives a high-speed optical signal, converts the high-speed optical signal to an electrical signal, and transmits the electrical signal to the multiplexer/demultiplexer unit4.

The type code acquisition unit11reads an optical module code4003, which is identification information indicating optical module type, from the optical module2. The monitoring controller7provides monitoring and control by exchanging control information4007such as the mode setting instruction4004and bandwidth allocation instruction4006, as well as monitoring result4008such as a monitoring result4005and the optical module code4003, with the function blocks.

The type code acquisition unit11is connected to the optical module2through a standard serial interface4001specified by Multi Source Agreement (MSA). The type code acquisition unit11acquires the optical module code4003from the optical module2of each type through the interface4001, and notifies the monitoring controller7of the acquired optical module code4003. The monitoring controller7is connected to the optical module2by a signal line other than the serial interface4001, in order to independently monitor implementation information4002from the optical module2.

The optical module code4003for determining the type of the optical module2, SFP or XFP type, is stored in advance within the optical module2. The method to acquire the type code through the serial interface4001is specified by MSA.

It is to be noted that the technology used in the embodiment is not necessarily compliant with MSA, and other methods than MSA may be used for acquiring the type code, accordingly.

The configuration of the multi-rate signal processing unit3ofFIG. 4will be described with reference toFIG. 5. InFIG. 5, the multi-rate signal processing unit3includes: six signal processors of an STM-64 processor50, an STM-16 processor51, an STM-4 processor52, an STM-1 processor53, an STM-0 processor54, and a 1000BASE-X processor55; a mode switching unit16; a clock generator17; a bandwidth allocation unit9; and a selector18.

The mode switching unit16notifies the function units of the signal type to be accommodated, in response to the mode setting instruction4004from the monitoring controller7. The clock generator17generates clock signals5010having a frequency necessary to operate each signal processor. The bandwidth allocation unit9inserts a dummy signal5008necessary for the unused bandwidth of a signal to be accommodated in an SDH/SONET frame. The selector18selects from parallel low-speed signals1to6(5002to5007), in response to a mode selection instruction5011from the mode switching unit16.

More specifically, the STM-64 processor50, STM-16 processor51, STM-4 processor52, STM-1 processor53, and STM-0 processor54respectively include: warning monitoring of STM-64 signal, STM-16 signal, STM-4 signal, STM-1 signal, and STM-0 signal, as well as monitoring process for the quality of the transmission lines. The 1000BASE-X processor55includes signal process that is compliant with IEEE802.3, failure monitoring of 1000BASE-X signal, and monitoring process for the quality of the transmission line.

The bandwidth allocation unit9operates the shared multiplexer/demultiplexer unit4independent of the signal to be accommodated, by inserting the dummy signal5008according to the signal type. The selector18and the multiplexer/demultiplexer unit4are connected with the parallel low-speed signal7(5012) in a fixed manner. In the case of multiplexing, the signal accommodation is performed by one of the signal processors50to55, using one of the parallel low-speed signals1to6(5002to5007) for the necessary bandwidth. The dummy signal5008is inserted for the other parallel low-speed signals to ensure the bandwidth of the multiplexer/demultiplexer unit4

The bandwidth allocation unit9sets parallel low-speed signals of a parallel low-speed signal, relative to a high speed of a signal that can be accommodated, and determines the number of parallel lines to be used by the parallel low-speed signal according to the signal type. The bandwidth allocation unit9inserts the dummy signal5008for the lack of the number of the determined parallel low-speed signals. This makes it possible to ensure connection to the multiplexer/demultiplexer unit4, independent of the signal type. In other words, because the amount of the high-speed signal output from the multiplexer/demultiplexer unit4is fixed, when the amount of the high-speed signal is not filled with the signals of the parallel low-speed signal, the bandwidth allocation unit9inserts the dummy signal so as to use the entire amount of the high-speed signal.

Further, the bandwidth allocation unit9allocates the first signal line of the data lines of the accommodation signal, to the first line of the parallel low-speed signal. On the other hand, in the case of demultiplexing, the bandwidth allocation unit9allocates the number of used parallel data lines corresponding to each of the operation modes, from the first line to the STM-64 processor50, STM-16 processor51, STM-4 processor52, STM-1 processor53, STM-0 processor54, and 1000BASE-X processor55, independent of the signal type. The bandwidth allocation unit9allocates the first line from the beginning of the STM-64 frame, and maps the STM-64 frame to OTU-2. On the other hand, the bandwidth allocation unit9demaps STM-64 from OTU-2, by allocating the first line of the parallel low-speed signal of the STM-64, to the first line of the accommodation signal. This makes demultiplexing easy by selecting the necessary number of used parallel data lines, without performing a signal processing.

A technology such as a method using Generic Framing Procedure (GFP) specified by ITU-T G. 7041, which is known as a versatile capsule technology, is standardized to accommodate a packet, which is a variable length frame represented by Ethernet, into an SONET/SDH network. Thus, the packet can be accommodated in SDH/SONET.

The process sequence using the multi-rate interface board1will be described with reference toFIG. 6. First, the type code acquisition unit11monitors the implementation state whether the optical module2, which is pluggable to an optical module cage, is installed to the multi-rate interface board (S6010). Upon implementation (S6011), the optical module2transmits an implementation notification to the type code acquisition unit11, in response to the state monitoring (S6012). The type code acquisition unit11transmits an optical module type information acquisition request (S6014). The optical module2returns an information notification to the type code acquisition unit11(S6015).

The type code acquisition unit11transmits an optical module type information notification to the monitoring controller7(S6017). Upon receiving the optical module type information notification, the monitoring controller7determines the operation mode (S6018), and transfers the optical module type information notification to a maintenance terminal6008(S6019). The maintenance terminal6008displays the optical module type on its display.

After determination of the operation mode, the monitoring controller7transmits an operation mode notification to the signal processing unit10(S6022). Upon receiving the operation mode notification, the signal processing unit10sets the operation mode (S6023). The signal processing unit10transmits a setting completion notification to the monitoring controller7(S6024). Upon receiving the setting completion notification, the monitoring controller7performs a bandwidth allocation determination (S6025). The monitoring controller7transmits a bandwidth setting notification to the bandwidth allocation unit9(S6026). Upon receiving the bandwidth setting notification, the bandwidth allocation unit9performs a bandwidth allocation setting (S6027), and transmits a setting completion notification to the monitoring controller7(S6028). Incidentally, the optical module type information is the same as the optical module code4003ofFIG. 4.

The monitoring controller7receives the optical module type information, and determines an operation mode7002from an operation mode definition table ofFIG. 7. Further, the monitoring controller7notifies the bandwidth allocation unit9of a used parallel number8004and unused parallel number8005in relation to the accommodation signal, from a parallel speed and signal expansion table ofFIG. 8. Then, the bandwidth allocation unit9inserts the dummy signal for the unused parallel number8005.

The definition table for determining the operation mode will be described with reference toFIG. 7. The monitoring controller7receives the type code of the optical module2acquired by the type code acquisition unit11. InFIG. 7, using the type code7001of the definition table7000as a search key, the monitoring controller7determines optical module type information7004and signal type information7005that correspond to the relevant type code. The monitoring controller7also determines the bandwidth allocation instruction7003from the signal type information7005. The bandwidth setting is made based on the maximum speed of the signal type to be accommodated. In the case of the definition table ofFIG. 7, STM-64 has the maximum speed, so that the bandwidth of STM-64 is set to be the maximum of the used bandwidth. The used bandwidth and the unused bandwidth are determined for each of the other signal types, relative to the bandwidth of STM-64.

The parallel speed and expansion number table will be described with reference toFIG. 8. InFIG. 8, a signal speed and expansion number table8000includes an operation mode8001, a parallel low-speed signal speed8002, a parallel low-speed signal expansion number8003, a used parallel number8004, and an unused parallel number8005. The parallel low-speed signal speed8002and the parallel low-speed signal expansion number8003are independent of the operation mode8001.

In the embodiment, the bandwidth setting is made based on the maximum speed of the signal type to be accommodated. The monitoring controller7determines the used parallel number8004and the unused parallel number8005, which are the information indicating the number of parallel expanded signals of the parallel low-speed signal depending on the signal type, based on the parallel low-speed signal expansion number8003, which is the expansion number of the maximum speed signal, and on the parallel low-speed signal speed8002, which is the speed of the parallel low-speed signal. In other words, STM-64 uses the entire bandwidth by the signals, and has no unused parallel number8005. The other operation modes, for example, the signal amount of STM-16 per unit hour is of one-fourth the STM-64, so that the ratio between the used parallel number and the unused parallel number is 1:3 for STM-16.

Here, as a specific example, a description will be given of the case in which the signal to be accommodated in an OTN frame of the standardized OTU-2, is STM-16. The configuration in the STM-16 signal processing will be described with reference toFIG. 9. InFIG. 9, the bandwidth allocation unit9receives the code of STM-16 from the bandwidth allocation instruction4006of the monitoring controller7. The bandwidth allocation unit9recognizes from the used parallel number8004that, of parallel low-speed signals (9004to9007) of 192 lines represented by line numbers a0to a191, the parallel low-speed signals (9004,9005) from the STM-16 signal processor51have 48 lines. Then, the bandwidth allocation unit9allocates the STM-16 signal to the parallel low-speed signals a0to a47(9004to9005). Further, the bandwidth allocation unit9determines that the unused parallel number of the STM-16 signal processor51is 144 lines, from the unused parallel number8005. Then, the bandwidth allocation unit9inserts the dummy signal of 144 lines generated by the bandwidth allocation unit9, to the line numbers a48to a191(9006to9007) of the 192-line parallel low-speed signals. As a result, the bandwidth allocation unit9configures the 192-line parallel low-speed signals a0to a191(9004to9007), and connects to the selector18. The selector18selects the parallel low-speed signals a0to a191(9004to9007) in response to a mode selection instruction5011, allocates the parallel low-speed signals a0to a47, to b0to b47of the parallel low-speed signals b0to b91(9008to9011) of the STM-64 frame in the multiplexer/demultiplexer unit4. Thus, STM-16 is accommodated in the STM-64 frame.

FIG. 10shows a typical frame of STM-64, andFIG. 11shows a frame of STM-64 in which STM-16 is accommodated. InFIG. 10, the STM-64 signal is a frame format prescribed in ITU-T G.707, and the signal includes: various overheads such as a relay section overhead (RSOH1000), a multiplex section overhead (MSOH1002), and a path overhead (POH1003); a pointer1001; and a payload1004in which user data is stored. Here, the multiplexer/demultiplexer unit accommodates the parallel speed signals b0to b91(1005to1009) into the entire STM-64 frame, in addition to the payload in which the user data of the STM-64 frame (17280 Bytes×9 Bytes) is stored.

InFIG. 11, when the STM-16 is accommodated in the STM-64 frame, the STM-16 signal is accommodated in b0(1005) to b47(1007) and the dummy signal is inserted to b48(1008) to b191(1009), and thus the STM-64 is configured.

The bandwidth process sequence, which is the feature of the embodiment, will be described with reference toFIG. 12. InFIG. 12, the implementation of the optical module2, namely, the installation of the optical module2to the interface board1(S1200), enables the monitoring controller7to determine the operation mode of the optical module2(S1201). More specifically, the monitoring controller7determines the operation mode7002corresponding to the acquired type code7001. Then, from the parallel speed and signal expansion table8000, the monitoring controller7determines the used parallel number8004and unused parallel number8005corresponding to the determined operation mode8001(S1202). Then, the monitoring controller7notifies the signal processor corresponding to the operation mode of the used parallel number8004, and notifies the bandwidth allocation unit9of the unused parallel number8005, respectively. Upon receiving the notification, the bandwidth allocation unit9inserts the dummy signal as parallel low-speed signals of the unused parallel number (S1203). As a result, the multi-rate signal processing unit3integrates into the maximum bandwidth of the maximum speed signal that can be accommodated, which is defined in the multi-rate interface board, independent of the signal type (S1204). Then, the multi-rate signal processing unit3transmits the signals to the multiplexer/demultiplexer unit4(S1205).

The demultiplexing operation of the multi-rate signal processing unit will be described with reference toFIG. 13. InFIG. 13, a multi-rate signal processing unit3A includes signal processors connected to the multiplexer/demultiplexer unit4, a selector18A, a clock generator17, and a mode switching unit16. The signal processors include STM-64 processor50A, STM-16 processor51A, STM-4 processor52A, STM-1 processor53A, STM-0 processor54A, and 1000BASE-X processor55A. The selector18A selects one of the outputs of the signal processors. The clock generator17supplies a clock to each of the signal processors. The mode switching unit16transmits a mode setting instruction5009to the signal processors, while transmitting the mode setting instruction5011to the selector18A and the clock generator17.

The parallel low-speed signal (50 Mbps) from the multiplexer/demultiplexer unit4is input to the STM-64 processor50A, STM-16 processor51A, STM-4 processor52A, STM-1 processor53A, STM-0 processor54A, and 1000BASE-X processor55A, respectively. The signal processors perform parallel/serial conversion using the low-speed signals for the used parallel number8004, from the first line of the parallel low-speed signal. It is to be noted that only the processor selected by the mode switching unit16, practically performs parallel/serial conversion. The output of the selected processor is selected by the selector18A, and is output from the multi-rate signal processing unit3A as the accommodation signal.

InFIG. 13, the monitoring signal for the processors is omitted. However, the monitoring result4005may be given to the monitoring controller7similarly as shown inFIGS. 4 and 5.

The functional blocks of the STM-16 processor will be described with reference toFIG. 14. It will be apparent to those skilled in the art that the other processors have the same functional blocks. InFIG. 14, the STM-16 processor51(51A) includes a serial/parallel converter511, a parallel/serial converter512, monitoring circuits513on the multiplexing side and on the demultiplexing side, and an ON/OFF controller514.

The serial/parallel converter511converts a serial accommodation signal5001to a parallel signal of 50 Mbits/s×48 corresponding to the STM-16 signal bandwidth, and outputs the parallel signal to the selector18. The parallel/serial converter512performs parallel/serial conversion on the 48-line low-speed signals (50 Mbits/s), which come from a multiplexer/demultiplexer unit7, from the first line of the parallel signal of 50 Mbits/s×192 corresponding to the STM-64 signal bandwidth, and transmits the serial signal to the selector18A. The multiplexing-side monitoring circuit513-1monitors the output of the serial/parallel converter511. The demultiplexing-side monitoring circuit513-2monitors the input of the parallel/serial converter512. The monitoring circuits513transmit the monitoring results to the monitoring controller7not shown. The ON/OFF controller514controls the operation and stopping of the STM-16 processor51(51A) based on the mode setting instruction from the mode switching unit16. Further, the serial/parallel converter511, the parallel/serial converter512, and the monitoring circuits513on the multiplexer and demultiplexing sides are all operated based on the clock from the clock generator17.

Since the operation of the bandwidth allocation unit9ofFIG. 14has been described above, its description will be omitted.

According to the first embodiment, it is possible to provide management using the standardized OTN frame, independent of the signal type. Further, perfect transmission is possible without terminating the signal to be accommodated, so that the client device can establish a network without regard to the transmission equipment.

Second Embodiment

In the first embodiment, the multi-rate signal processing unit3allocates the first signal line of the data lines of the accommodation signal, to the first line of the parallel low-speed signal, independent of the signal type to be accommodated. On the other hand, in the case of demultiplexing, the multi-rate signal processing unit3allocates the number of used parallel data lines corresponding to each of the operation modes, to the STM-64 processor, STM-16 processor, STM-4 processor, STM-1 processor, STM-0 processor, and 1000BASE-X processor. Then, the selector selects the signal to be accommodated. However, the first line is used independent of the signal type in demultiplexing, thereby making the selector configuration complicated. In a second embodiment, a description will be given of the execution method in a configuration with no selector.

Referring toFIG. 15, a description will be given of the configuration of a multi-rate signal processing unit100in the second embodiment. InFIG. 15, the multi-rate signal processing unit100includes: five signal processors of an STM-16 processor101, an STM-4 processor102, an STM-1 processor103, an STM-0 processor104, and a 1000BASE-X processor105; a mode switching unit116for setting an operation mode to the signal processors101to105, in response to a mode setting instruction4004from the monitoring controller7; and a clock generator117for generating a clock signal1311having a frequency necessary to operate a selected signal processor.

The multi-rate signal processing unit100and the multiplexer/demultiplexer unit4are connected with parallel low-speed signals a0to a191(1301to1313) at a fixed rate. However, the signal is accommodated in the fixed lines of the parallel low-speed signals a0to a191(1301to1313) according to the signal type. In other words, the multi-rate signal processing unit100allocates the parallel low-speed signal of the STM-16 processor101to the parallel low-speed signals a0to a47(1301to1302), the parallel low-speed signal of the STM-4 processor102to the parallel low-speed signals a48to a59(1303to1304), the parallel low-speed signal of the STM-1 processor103to the parallel low-speed signals a60to a62(1305to1306), the parallel low-speed signal of the STM-0 processor104to the parallel low-speed signal a63(1307), and the parallel low-speed signal of the 1000BASE-X processor105to the parallel low-speed signals a64to a111(1308to1309), respectively.

On the other hand, in the case of demultiplexing, the multi-rate processing unit100allocates, of the parallel low-speed signals a0to a191(1301to1313), a0to a47(1301to1302) to the STM-16 processor101, a48to a59(1303to1304) to the STM-4 processor102, a60to a62(1305to1306) to the STM-1 processor103, a63(1307) to the STM-0 processor104, and a64to a111(1308to1309) to the 1000BASE-X processor105, respectively, according to the signal type.

As described above, the multi-rate signal processing unit100allocates the first line from the beginning of the STM-64 frame, when mapping the STM-64 frame to OTU-2. This makes it possible, in the case of demapping of the STM-64 from OTU-2, to allocate the first line of the parallel low-speed signal of STM-64, to the first line of the accommodation signal. As a result, this facilitates demultiplexing by selecting the necessary number of used parallel data lines, without performing a signal processing. Thus, unlike the first embodiment, there is no need to configure the bandwidth allocation unit as well as the selector.

FIG. 16shows a frame format in the application of the second embodiment. InFIG. 16, the parallel low-speed signals a0to a191(1301to1313) are mapped as follows: a0to a47, to STM-16 signal1401; a49to a59, to STM-4 signal1402; a60to a62, to STM-1 signal1403; a63to STM-0 signal1404; a64to a111, to 1000BASE-X signal1405; and a112to a191, to dummy signal1406, independent of the signal to be accommodated. The add/drop position varies in the STM-64 frame depending on the signal type. Thus, it is necessary to acquire data of a desired position according to the type code, in order to demultiplex the data.

According to the second embodiment, a single multi-rate interface board is used to realize a network capable of accommodating a wide range of signal speeds to the standardized OTN frame, and of transmitting the input signal as it is. Because the interface board can accommodate various types of signals, it is possible to flexibly change the network configuration only by the implementation of the optical module of the embodiment, or by the operation from the upper controller. In addition, because the input signal is perfectly transmitted without being terminated, it is possible to establish a network without regard to the transmission equipment.

Further, according to the embodiment, the multi-rate interface board capable of accommodating various types of signals is used in a network in which various signals exist. This reduces the number of components, allowing the change of the signal type to be processed in the interface board, only by the operation from the upper controller or by the implementation of the optical module. Thus, a replacement operation of the interface board can be omitted in the case of an unexpected change of the network configuration. The accommodation to the OTN frame is performed at a fixed rate, so that the multi-rate interface board can be realized with an inexpensive configuration without the need to implement a separate OTN processor for each signal to be accommodated.