Patent Description:
Passive optical networks are used extensively in telecommunication systems to provide high-speed optical communications between an optical line terminal (OLT) and a plurality of optical network terminals (ONTs). The OLT typically has a socket into which an optical module may be inserted. Such a module has an optical transceiver that may be used to communicate optical signals with the ONTs through optical fibers of the PON. In the downstream direction, the optical transceiver receives downstream data from the OLT and converts this data from the electrical domain to the optical domain for transmission to the ONTs. In the upstream direction, the optical transceiver receives data in the optical domain from the ONTs and converts the data into the electrical domain for transmission to the OLT. Thus, the optical module has an electrical connector that plugs into the socket of the OLT. This electrical connector comprises a plurality of pins that make electrical connections with circuits of the OLT to allow electrical communication between the OLT and the optical transceiver of the optical module.

Currently, there are several different optical protocols that may be used for optical communication across a PON, such as Gigabit-capable Passive Optical Network (GPON) and XGS-PON, for example. Typically, an optical module is configured to support a certain protocol. However, some optical modules are of a type capable of supporting multiple optical protocols. As an example, a Multi-PON module may simultaneously or separately support both GPON and XGS-PON.

The electrical connectors of optical modules of different types for supporting different optical protocols or combinations of optical protocols typically have the same mechanical specifications but may have different electrical and operational specifications. That is, the pin functionality and electrical requirements for optical modules of different types are typically different depending on the optical protocol or combination of optical protocols that are supported by the module. Thus, from an electrical perspective, the pin layout for an optical module of one type is typically different than the pin layout for an optical module of a different type, even though mechanically the pin layouts are the same. As an example, a pin at a given pin position for a GPON optical module may need to be grounded but a pin at the same pin position for a multi-PON optical module might carry high-speed data. As a result of different electrical and operational requirements across optical modules of different types, an OLT compatible with one type of optical module is typically incompatible with a different type of optical module.

<CIT> discloses an optical module and an optical line terminal device. The optical module comprises a housing, a circuit board arranged in the housing and provided with an electrical interface, an optical assembly arranged in the housing and a memory unit arranged in the housing. The optical assembly is configured to be connected with the circuit board electrically and to perform signal transformation between an optical signal and an electrical signal. The memory unit is configured to be connected with the circuit board electrically and to store an operation parameter of the optical assembly.

The present invention provides an optical line terminal as claimed in claim <NUM> and a method as claimed in claim <NUM>.

The disclosure can be better understood with reference to the following drawings. The elements of the drawings are not necessarily to scale relative to each other, emphasis instead being placed upon clearly illustrating the principles of the disclosure. Furthermore, like reference numerals designate corresponding parts throughout the several views.

The present disclosure generally pertains to optical line terminal (OLT) circuitry that can be controlled to be compatible with optical modules of different optical protocols having different electrical connectivity requirements. In some embodiments, an OLT has a controller that is configured to communicate with an optical module plugged into or otherwise mated with a socket of the OLT in order to discover the module's type. Based on the detected module type, the controller is configured to control the electrical characteristics of the OLT circuitry so that it is compatible with the electrical and operational requirements of the optical module. Thus, the OLT is compatible for use with any of a plurality of optical module types.

<FIG> depicts an exemplary embodiment of an optical network <NUM>. In some embodiments, the network <NUM> of <FIG> is a passive optical network (PON), but other types of optical networks are possible in other embodiments. As shown by <FIG>, the optical network <NUM> has an optical line terminal (OLT) <NUM> that is optically coupled to a plurality of optical network terminals (ONTs) <NUM>. In this regard, the OLT <NUM> is coupled to an optical splitter <NUM> by at least one optical fiber <NUM>, and the splitter <NUM> is coupled to the ONTs <NUM> by optical fibers <NUM>. As an example, the optical network <NUM> may form part of a telecommunication system where the OLT <NUM> is positioned at a central office of a telecommunication network or an intermediate point between the central office and a plurality of customer premises. Each ONT <NUM> may be positioned at or near a respective customer premises. However, other locations of the OLT <NUM> and ONTs <NUM> and other uses of the optical network <NUM> are possible in other embodiments.

In the downstream direction, the OLT <NUM> is configured to receive data to be transmitted to the ONTs <NUM>. As an example, the OLT <NUM> may receive data from a network (not shown), such as the Internet or some other type of network for communicating data. The OLT <NUM> is further configured to encapsulate the data in accordance with the optical protocol of the network <NUM> and to transmit frames containing such data via at least one optical signal through the optical fiber <NUM> connected to the OLT <NUM>. An optical signal carrying frames from the OLT <NUM> is split by the splitter <NUM> so that is received by each of the ONTs <NUM>. Each ONT <NUM> extracts the transmitted downstream data from the received frames and transmits the data, as appropriate, further downstream, such as to customer premises equipment (CPE) (not shown) at a one more customer premises or other types of communication devices.

In the upstream direction, each ONT <NUM> receives data to be communicated to the OLT <NUM>. As an example, an ONT <NUM> may receive data from CPE at one or more customer premises or other communication devices. The ONT <NUM> is further configured to encapsulate the data in accordance with the optical protocol of the network <NUM> and to transmit such data via at least one optical signal through the optical fiber <NUM> connected to the ONT <NUM>. The optical signals transmitted by the ONTs <NUM> pass through the splitter <NUM> and the optical fiber <NUM> and are received by the OLT <NUM>. The OLT <NUM> extracts the transmitted upstream data and transmits the data, as appropriate, further upstream, such as to a network (e.g., the Internet or other type of network).

Communication in the upstream direction is time-division multiplexed, under the control of the OLT <NUM>, so as to prevent interference between the transmissions of the ONTs <NUM>. In this regard, the OLT <NUM> may communicate with the ONTs <NUM> via a control channel of the optical protocol of the network <NUM> and assign each ONT <NUM> with timeslots in which to transmit in the upstream direction. In other embodiments, other techniques for communicating between the OLT <NUM> and ONTs <NUM> are possible. As an example, it is possible for the ONTs <NUM> to transmit in the upstream direction at different wavelengths (i.e., wavelength-division multiplexing) such that time-division multiplexing between the ONTs <NUM> is unnecessary.

<FIG> depicts an exemplary embodiment of the OLT <NUM>. As shown by <FIG>, the OLT <NUM> comprises OLT circuitry <NUM> comprising an adapter <NUM> that is electrically connected to at least one socket <NUM>. For illustrative purposes, the OLT <NUM> of <FIG> is shown with a single socket <NUM>, but the OLT <NUM> may have any number of sockets in other embodiments. The socket <NUM> has a slot for receiving an optical module <NUM> having an optical transceiver <NUM>. The OLT <NUM> also has a controller <NUM> that is configured to control the adapter <NUM>, as will be described in more detail below.

The OLT circuitry <NUM> is configured to control the operation of the OLT <NUM> and the communications occurring on the optical network <NUM>. As an example, the OLT circuitry <NUM> may comprise a Media Access Controller (MAC) <NUM> that, according to techniques known in the art, is configured to encapsulate downstream data and de-encapsulate upstream data in accordance with the optical protocol of the network <NUM>. The MAC <NUM> may also communicate with the ONTs <NUM> to assign upstream timeslots, as described above.

The MAC <NUM> is configured to provide one or more electrical signals, such as one or more control signals and at least one data signal defining data to be transmitted downstream to the ONTs <NUM>. The adapter <NUM> is configured to receive and process these electrical signals so that the electrical signals are compatible with the optical module <NUM>. The optical transceiver <NUM> is configured to modulate an optical signal with the downstream data defined by at least one electrical signal from the adapter <NUM>, thereby converting the downstream data from the electrical domain to the optical domain. The transceiver <NUM> is optically coupled to the optical fiber <NUM> (<FIG>) and transmits the modulated optical signal through the optical fiber <NUM> to the ONTs <NUM>.

The transceiver <NUM> is also configured to receive upstream optical signals from the optical fiber <NUM> and to recover the upstream data carried by these signals, thereby converting such data from the optical domain to the electrical domain. One or more control signals and at least one electrical signal defining such data are transmitted from the optical module <NUM> to the adapter <NUM>, which forwards the upstream data to other components of the OLT circuitry <NUM>, such as the MAC <NUM>, for processing.

As shown by <FIG>, the optical module <NUM> may have a printed circuit board (PCB) <NUM>, sometimes referred to as a "card," on which other components of the module <NUM> may reside. Notably, the optical module <NUM> is detachably coupled to the socket <NUM> of the OLT <NUM> so that it can be removed from the socket <NUM> by pulling the optical module <NUM> by hand or otherwise. In this regard, as shown by <FIG>, the optical module <NUM> has an electrical connector <NUM> that can be plugged into or otherwise mated with the socket <NUM> to form an electrical connection between the optical module <NUM> and other components of the OLT <NUM>, such as the adapter <NUM> and controller <NUM>.

As an example, the electrical connector <NUM> may have a plurality of conductive pins (not shown in <FIG>) that are respectively inserted into female receptacles of the socket <NUM> to mate the connector <NUM> with the socket <NUM>. Each receptacle of the socket <NUM> may have a hole for receiving a corresponding pin of the connector <NUM>, and an inner wall of the hole may be plated with conductive material to form an electrical connection between the pin and the receptacle.

Depending on the optical protocol employed, one or more of the pins of the connector <NUM> may carry an electrical signal to the adapter <NUM>, and one or more of the pins may receive an electrical signal from the adapter <NUM>. The specifications for the optical module <NUM> may indicate the type of signals to be carried by each pin and may also require certain electrical characteristics of the device that is connected to the connector <NUM>. For example, the specifications may indicate which pin is to carry upstream data (including voltage, current, and data rate requirements) and which pin is to carry downstream data (including voltage, current, and data rate requirements). The specifications may also require one or more pins to be connected to ground or a power supply. The specifications may further require that some pins are to carry certain control signals. As an example, the specifications may indicate that one of the pins is for transmitting from the optical module <NUM> a "transmit fault" signal indicating whether there is a detected fault for the optical transmitter of the transceiver <NUM>. There are many other electrical characteristics and signal types of the pins that may be required by the module's specifications in other examples.

To be electrically and operationally compatible with the optical module <NUM>, the device connected to it must satisfy the electrical requirements of the module's specifications and also have circuits capable of processing the signals received from and transmitted to the optical module <NUM>. Failing to adhere to the electrical requirements of the specifications or connecting a device incompatible with the electrical specifications may result in damage either to the optical module <NUM> or a device connected to it depending on the nature of the incompatibility.

As used herein, "electrical compatibility" refers to a device that satisfies the electrical requirements specified for a module <NUM>, such as voltage levels and current levels. Violation of the electrical requirements may result in damage or hazardous conditions. "Operational compatibility" refers to a device that satisfies the operational requirements specified for a module <NUM>, such as the types of signals to be communicated. As an example, an operational requirement may be that a pin is to carry a certain signal, such as a data signal or a certain control signal, whereas the electrical requirements for the pin may refer to the signal's acceptable voltage or current range. Thus, to be operationally compatible with the module <NUM>, a device should process signals to be transmitted to or received from the module <NUM> such that operation of the device and module <NUM> is successful for communicating across the optical network <NUM>. "Mechanical compatibility" refers to a device that is capable of physically mating with the module <NUM>. Thus, a device that is mechanically compatible with the module <NUM> should have a socket <NUM> with a receptacle layout that corresponds to the pin layout for the connector <NUM> so that the connector <NUM> successfully mates with the socket where each pin is received by a respective receptacle.

To connect the optical module <NUM> with other components of the OLT <NUM>, the optical module <NUM> may be inserted by hand or otherwise into a slot of the socket <NUM> such that the pins of the connector <NUM> align with the receptacles of the socket <NUM>. As the connector <NUM> and socket <NUM> are mated, each pin of the connector <NUM> is received by a respective receptacle of the socket <NUM> and makes electrical contact with a circuit of the OLT <NUM>. Note that there are various types of conventional connectors and sockets that may be used to electrically connect the optical module <NUM> with other components of the OLT <NUM>.

As shown by <FIG>, the optical module <NUM> has an optical port <NUM> that may be coupled to an optical fiber <NUM> (<FIG>). The optical module <NUM> also has an interface circuit <NUM> and memory <NUM> electrically connected to the connector <NUM> (e.g., electrically connected to one or more pins of the connector <NUM>) to enable a device external to the module <NUM>, such as the controller <NUM> (<FIG>), to access data <NUM> stored in memory <NUM>. For illustrative purposes, this data will be referred to hereafter as "module data. " In some embodiments, the module data <NUM> may be used to determine a type of the optical module <NUM>, such as the optical protocol used by the optical module <NUM> for communication over the optical network <NUM>. As an example, the module data <NUM> may include a type identifier that identifies the module type of the module <NUM>, such as the optical protocol or combination of optical protocols supported by the module <NUM>. In some embodiments, the module data <NUM> defines another type of identifier, such as a serial number (e.g., a part or model number) of the module <NUM>, and this serial number or other identifier may be used to lookup or otherwise determine the module type.

In some embodiments, the module data <NUM> is stored in a register <NUM> that is accessible through the connector <NUM> via I<NUM>C protocol. In this regard, the interface circuit <NUM> may be compatible with I<NUM>C protocol such that it responds to an I<NUM>C command submitted through the connector <NUM> to retrieve the module data <NUM> from the register <NUM> and return the retrieved module data <NUM>. As will be described in more detail below, the controller <NUM> may be configured to communicate with the interface circuit <NUM> to receive the module data <NUM> and use the module data <NUM> for determining a type of the optical module <NUM> inserted into the socket <NUM>. In other embodiments, other techniques and protocols for accessing the module data <NUM> are possible.

As an example, when a user mates the optical module <NUM> with the socket <NUM>, the user may manually input or otherwise send to the OLT <NUM> (wirelessly transmit or transmit through a data port of the OLT <NUM>) data indicative of the type of optical module <NUM> mated with the socket <NUM>. In some embodiments, the OLT <NUM> may have one or more switches or buttons (not shown) that may be used by a user for indicating the type of optical module <NUM> mated with the socket <NUM>. Yet other techniques for enabling the controller <NUM> to determine the type of optical module <NUM> mated with the socket <NUM> are possible.

As noted above, the optical module <NUM> may implement any of a variety of optical protocols for communication over the optical network <NUM>. As an example, the optical module <NUM> may utilize GPON, XGS-PON, or a combination of optical protocols, such as a combination of GPON and XGS-PON, referred to in the art as "Multi-PON. " Note that, as used herein, "GPON" refers to an optical protocol in accordance with the GPON standard, including different versions of the GPON standard; "XGS-PON" refers to an optical protocol in accordance with the XGS-PON standard, including different versions of the XGS-PON standard; and Multi-PON refers to an optical protocol in accordance with the Multi-PON standard, including different versions of the Multi-PON standard. In other embodiments, the optical module <NUM> may utilize other types of optical protocols or combinations of optical protocols for communication across the network <NUM>.

By detachably coupling the optical module <NUM> to the socket <NUM>, as described above, it is possible to remove the optical module <NUM> by hand or otherwise as may be desired. For example, in the event of a fault on the optical module <NUM>, the module <NUM> may be removed and replaced with a new module <NUM>. However, if the OLT <NUM> is electrically incompatible with the module <NUM> that is mated with the socket <NUM>, then components of the OLT <NUM> may be damaged or errors in the operation of the OLT <NUM> may occur.

In some embodiments, the adapter <NUM> is configurable to operate in different modes under the control of the controller <NUM> so that it operates in a compatible manner with the optical module <NUM> that is inserted into the socket <NUM>, as will be described in more detail below. <FIG> depicts an exemplary embodiment of the controller <NUM>.

As shown by <FIG>, the controller <NUM> comprises control logic <NUM> and control circuitry <NUM> for generally controlling the operation of the controller <NUM>, as will be described in more detail hereafter. The control circuitry <NUM> is implemented in hardware, such as a field programmable gate array (FPGA), for example. The control logic <NUM> can be implemented in software, hardware, firmware or any combination thereof. In the exemplary controller <NUM> illustrated by <FIG>, the control logic <NUM> is implemented in software and stored in memory <NUM> of the controller <NUM>.

Note that the control logic <NUM>, when implemented in software, can be stored and transported on any computer-readable medium for use by or in connection with an instruction execution apparatus that can fetch and execute instructions. In the context of this document, a "computer-readable medium" can be any means that can contain or store a computer program for use by or in connection with an instruction execution apparatus.

The exemplary controller <NUM> depicted by <FIG> comprises at least one conventional processor <NUM>, such as a digital signal processor (DSP) or a central processing unit (CPU), that communicates to and drives the other elements within the controller <NUM> via a local interface <NUM>, which can include at least one bus and at least one control signal. The local interface <NUM> may be electrically connected to the OLT circuitry <NUM> (<FIG>), including in particular the adapter <NUM>, and socket <NUM> to enable communication with these components, as well as the interface circuit <NUM> (<FIG>).

As shown by <FIG>, the memory <NUM> stores configuration data <NUM> and module type data <NUM> that are used by the control logic <NUM> and/or the control circuitry <NUM> for controlling the adapter <NUM> (<FIG>). As will be described in more detail below, the module type data <NUM> includes information that enables the module type for the module <NUM> to be identified based on the module data <NUM> (<FIG>). As an example, the module type data <NUM> may define a table that correlates an identifier from the module data <NUM> with a type identifier indicative of a module type of the module <NUM>.

The configuration data <NUM> indicates how the adapter <NUM> is to be configured or otherwise controlled by the controller <NUM> in order to place the adapter <NUM> in the desired mode of operation, as will be described in more detail hereafter. In this regard, based on the configuration data <NUM>, the controller <NUM> may transmit to the adapter <NUM> control signals for controlling the components of the adapter <NUM>, and the configuration data <NUM> may indicate the states of the control signals so that the adapter <NUM> operates in the desired mode. As an example, the control signals may be used to turn on or off certain transistors, or the control signals may be transmitted to multiplexers or switches to control the switching functionality of these components (e.g., control which input is selected for output by a multiplexer or whether a switch is in an open state or a closed state).

In some embodiments, the controller <NUM> is configured to selectively control the adapter <NUM> to work in a plurality of modes of operation where each mode of operation corresponds to a specific optical protocol or combination of optical protocols. Further, when the adapter <NUM> is placed in a given mode of operation, the controller <NUM> controls the adapter <NUM> so that it is electrically and operationally compatible with a module that supports the optical protocol or combination of optical protocols corresponding to the mode of operation.

As an example, one of the modes of operation may correspond to GPON and another mode of operation may correspond to XGS-PON. When an optical module <NUM> of a type that communicates in accordance with GPON is inserted into the socket <NUM>, the controller <NUM> controls the adapter <NUM> so that it is electrically and operationally compatible with such optical module <NUM>. That is, the electrical and operational characteristics of the adapter <NUM> are controlled so that these characteristics meet the electrical and operational specifications for interfacing with a GPON module.

However, when an optical module <NUM> of a type that communicates in accordance with XGS-PON is inserted into the socket <NUM>, the controller <NUM> controls the adapter <NUM> so that it is electrically and operationally compatible with such optical module <NUM>. That is, the electrical and operational characteristics of the adapter <NUM> are controlled so that these characteristics meet the electrical and operational specifications for interfacing with an XGS-PON module.

Note that that the controller <NUM> can be configured to control the adapter <NUM> to be suitable for use in conjunction with any desired module type. As an example, in addition to supporting GPON and XGS-PON, the controller <NUM> is configured to control the adapter <NUM> to be suitable for use with a Multi-PON module. Yet other types of optical modules <NUM> supporting other optical protocols or combinations of protocols in addition to or in lieu of the optical protocols specifically described herein may be supported in other embodiments.

Note that the controller <NUM> is shown in <FIG> as separate from the OLT circuitry <NUM>, including the MAC <NUM> and the adapter <NUM>. However, it should be emphasized that the controller <NUM> may form part of the circuitry implemented within the OLT <NUM> and, in fact, may be integrated with and/or share hardware (e.g., memory, processors, etc.) with components of the OLT circuitry <NUM> shown by <FIG>, including components of the adapter <NUM> and/or the MAC <NUM>. As an example, in some embodiments, the controller <NUM> or at least portions of the controller <NUM> may be implemented in an FPGA structure along with at least portions of the OLT circuitry <NUM> shown by <FIG>, including at least portions of the MAC <NUM> and/or the adapter <NUM>. In other embodiments, other configurations and techniques for implementing the OLT circuitry <NUM> shown by <FIG> and the controller <NUM> are possible.

In addition to the modes corresponding to optical protocols described herein, the controller <NUM> may be configured to control the adapter <NUM> to work in a mode, referred to herein as the "safe mode. " In the safe mode, the controller <NUM> controls the adapter <NUM> so that it is electrically compatible with any module type supported by the OLT <NUM> for preventing circuit damage or unsafe operating conditions. In such mode, the adapter <NUM> is mechanically and electrically compatible with each type of supported module <NUM> but might not be operationally compatible with any such type of module <NUM>. That is, in the safe mode, the adapter <NUM> is electrically compatible with any module of a type that is supported by the OLT <NUM> but successful operation for communicating across the optical network <NUM> may not occur until the adapter <NUM> is transitioned out of the safe mode and into a mode that is operationally compatible with the module <NUM>, as will be described in more detail below. As a mere example, in the safe mode, the adapter <NUM> might electrically disconnect a given receptacle so as to prevent circuit damage irrespective of which module type is mated with the socket <NUM>, but in another mode of operation, the adapter <NUM> might electrically connect the same receptacle to a circuit for transmitting a control signal to an optical module <NUM> mated with the socket <NUM> depending on the operational requirements of such module <NUM>.

To illustrate the foregoing in more detail assume that, for a particular pin of the connector <NUM> (<FIG>), the specifications for a given optical module <NUM> specify a certain signal type. For example, the specifications may specify that the pin is to carry a control signal for indicating a certain condition. In the safe mode, the adapter <NUM> might not be configured to control the signal transmitted to such pin for indicating the condition, but the pin would be connected to a circuit of the adapter <NUM> that satisfies the electrical requirements for the pin, such as the maximum voltage or current, for example. Thus, while in the safe mode, the adapter <NUM> does not satisfy the signal type requirement for the pin but does satisfy the pin's electrical requirements for preventing circuit damage or unsafe operating conditions in the OLT <NUM>. That is, in the safe mode, the adapter <NUM> is electrically compatible with the pin but not operationally compatible since it is not configured to transmit the specified signal type to the pin.

The safe mode may be used, for example, when there is no optical module <NUM> mated with the socket <NUM> to help ensure that damage or hazardous conditions do not occur when an optical module <NUM> is inserted into the socket <NUM>. In this regard, there may be a finite amount of time that elapses between the time that an optical module <NUM> is inserted into the socket <NUM> and the time that the adapter <NUM> transitions into the operational mode corresponding to the module's type, as will be described in more detail below. If the adapter <NUM> is in the safe mode before the optical module <NUM> is mated with the socket <NUM>, then operation of the adapter <NUM> in the safe mode prevents damage or unsafe operating conditions after insertion of the module <NUM> but prior to successful transition of the adapter <NUM> into the appropriate mode (i.e., the mode corresponding to the module's type) regardless of the type of optical module <NUM> that is inserted into the socket <NUM>. In some embodiments, depending on the types of optical modules <NUM> supported, the controller <NUM> may configure the adapter <NUM> for safe mode upon power up or reboot initialization.

The safe mode may also be used when the optical module <NUM> inserted into the socket <NUM> is of a type that is not supported by the OLT <NUM> or is unrecognizable. In the safe mode, the adapter <NUM> may be configured to source to the optical module <NUM> or sink from the optical module <NUM> only a small amount of current (such as about <NUM> mill-Amperes or less) so that damage to the optical module <NUM> and the OLT <NUM> is prevented.

To enable the controller <NUM> to determine which operational mode is appropriate, the control circuitry <NUM> may be configured to detect when an optical module <NUM> is electrically mated with the socket <NUM>, as will be described in more detail below. In some embodiments, the control circuitry <NUM> checks for a presence of an optical module <NUM> in the socket <NUM> frequently, such as every <NUM> milliseconds (ms), for example, so that the adapter <NUM> is quickly transitioned to the safe made when an optical module <NUM> is removed from the socket <NUM>. This helps to reduce the likelihood that another optical module <NUM> will be inserted into the socket <NUM> before the adapter <NUM> is transitioned to the safe mode.

When the control circuitry <NUM> determines that an optical module <NUM> has been inserted into and electrically mated with the socket <NUM>, the control circuitry <NUM> is configured to communicate with the optical module <NUM> to determine information indicative of the type of module <NUM> that is mated with the socket <NUM>. As an example, the control circuitry <NUM> may receive from the optical module <NUM> an identifier that identifies the module type or other information, such as a model or part number that may be used to identify the type of optical module <NUM> mated with the socket <NUM>.

Note that there are various techniques and protocols that may be used by the control circuitry <NUM> to detect an optical module <NUM> and determine information indicative of module type. In some embodiments, the control circuitry <NUM> is configured to communicate with the optical module <NUM> in accordance with I<NUM>C protocol. In this regard, periodically (such as every <NUM> or some other time period), the control circuitry <NUM> is configured to transmit through the connector <NUM> (<FIG>) to the interface circuit <NUM> an I<NUM>C request to read an I<NUM>C register <NUM> of the optical module <NUM>. If no optical module <NUM> is in the socket <NUM>, then the control circuitry <NUM> will not receive a valid value in response to the read request. In such case, the control circuitry <NUM> determines that an optical module <NUM> is not inserted into the socket <NUM> and ensures that the adapter <NUM> is in the safe mode.

However, if an optical module <NUM> is electrically mated with the socket <NUM>, then the interface circuit <NUM> (<FIG>) in response to the read request from the control circuitry <NUM> retrieves the module data <NUM> stored in the I<NUM>C register <NUM> and returns the module data <NUM> to the control circuitry <NUM> in an I<NUM>C reply. In such case the control circuitry <NUM>, based on receiving valid module data <NUM>, determines that an optical module <NUM> is mated with the socket <NUM> and forwards the module data <NUM> to the control logic <NUM> for further processing.

Based on the received module data <NUM>, the control logic <NUM> is configured to determine the type of module inserted into the socket <NUM> and then control the adapter <NUM> to place it in the mode corresponding to the module type. Note that there are various techniques that can be used to select the operational mode for the adapter <NUM> based on module type. In some embodiments, the module data <NUM> defines a part or model identifier of the optical module <NUM> and the module type data <NUM> defines a table that maps each part or model identifier to an identifier of the module type to be used in selecting the mode of operation. Thus, the control logic <NUM> may use the part or model identifier from the module data <NUM> as a key to look up the module's type and then select, based on module type, the operational mode for the adapter <NUM> so that it is electrically and operationally compatible with the optical module <NUM>. The control logic <NUM> then causes the controller <NUM> to send to the adapter <NUM> control signals for transitioning the adapter <NUM> to such mode, as will be described in more detail below.

Thus, when an optical module <NUM> is inserted into and electrically mated with the socket <NUM>, the adapter <NUM> should be operating in the safe mode, and the presence of the optical module <NUM> is detected by the control circuitry <NUM>. The control logic <NUM> then controls the adapter <NUM> to transition it from the safe mode to an operational mode that is electrically and operationally compatible with the optical module <NUM>. In this regard, as will be described in more detail below, the configuration data <NUM> may indicate how the adapter <NUM> is to be controlled (e.g., specify the types of control signals to be transmitted to the adapter <NUM>) for placing the adapter <NUM> in the desired mode of operation. Once transitioned to the desired mode of operation, the adapter <NUM> should remain in this operational mode until the optical module <NUM> is pulled from the socket <NUM> at which point the control circuitry <NUM> quickly detects removal of the module <NUM> from the socket <NUM> and transitions the adapter <NUM> to the safe mode.

Note that using the control circuitry <NUM> to detect the presence of an optical module <NUM> and transition the adapter <NUM> to the safe mode when the module is removed from the socket <NUM> helps to ensure that the adapter <NUM> is quickly transitioned to the safe mode, when appropriate, since the control circuitry <NUM> is implemented in hardware (e.g., an FPGA). Further, using software to select the desired mode of operation for an optical module <NUM> may have several advantages such as facilitating processing of a large amount of data and facilitating updates to the configuration data <NUM> and the module type data <NUM>. As an example, the configuration data <NUM> may be updated to change the manner in which the adapter <NUM> is to be controlled for a given mode of operation (including possibly adding additional modes of operation).

In addition, the selection of a mode of operation and transition of the adapter <NUM> to the selected mode of operation by the control logic <NUM> after insertion of a module <NUM> into the socket <NUM> is not generally as time sensitive as the transitioning of the adapter <NUM> to the safe mode performed by the control circuitry <NUM> when the module <NUM> is removed from the socket <NUM>. Thus, using hardware to perform the functions described herein for the control circuitry <NUM> and software to perform the functions described herein for the control logic <NUM> has various advantages, but performing the ascribed functions in this manner is unnecessary in other embodiments. Indeed, it is possible for any of the functions described herein as being performed by the control logic <NUM> to be performed by the control circuitry <NUM>, and it is possible for any of the functions described herein as being performed by the control circuitry <NUM> to be performed by the control logic <NUM>.

Further, there are various techniques that may be used by the controller <NUM> to control the adapter <NUM> as described herein. In this regard, as indicated above, the control signals from the controller <NUM> may be transmitted to and control components of the adapter <NUM>, such as to turn on or off certain transistors or control the states of switches, multiplexers, or other types of circuitry of the adapter <NUM>. To better illustrate some of these concepts, exemplary techniques for controlling components of the adapter <NUM> will be described in more detail below with reference to <FIG>. However, it should be emphasized that the techniques described below are presented for illustrative purposes, and other techniques are possible in other embodiments.

<FIG> shows a plurality of pins <NUM> of the connecter <NUM> (<FIG>) for an optical module <NUM> that is electrically mated with the socket <NUM>. As shown by <FIG>, each pin <NUM> is electrically connected to respective adapter circuitry <NUM> of the adapter <NUM> through a respective receptacle <NUM> into which the pin <NUM> is inserted. Each set of adapter circuitry <NUM> may be electrically connected to circuitry (not shown in <FIG>) of the optical module <NUM> through a respective pin <NUM> and receptacle <NUM> pair and may also be electrically connected to other components of the OLT circuitry <NUM>, such as the MAC <NUM>. The adapter circuitry <NUM> may receive and process an electrical signal from either another component of the OLT circuitry <NUM> (e.g., the MAC <NUM>) or the optical module <NUM> and may transmit a processed electrical signal to either another component of the OLT circuitry <NUM> (e.g., the MAC <NUM>) or the optical module <NUM> depending on the type of module <NUM> mated with the adapter <NUM>.

<FIG> depicts an exemplary embodiment of adapter circuitry <NUM>. In the exemplary embodiment depicted by <FIG>, the adapter circuitry <NUM> comprises a plurality of circuits <NUM>-<NUM>, referred to herein as "Mode A circuit," "Mode B circuit," and "Safe Mode circuit. " The Mode A circuit <NUM> is electrically and operationally compatible with a first type of optical module <NUM>, such as a GPON module for example, for operation in a first mode. The Mode B circuit <NUM> is electrically and operationally compatible with a second type of optical module <NUM>, such as XGS-PON for example, for operation in a second mode. Further, the Safe Mode circuit <NUM> is electrically but not operationally compatible with both types of optical modules <NUM> for operation in the safe mode. In other embodiments, the Safe Mode circuit <NUM> is not needed, depending on the type of optical modules <NUM> that are supported. In other embodiments, any number of circuits compatible with any number of optical module types may be connected to the multiplexer <NUM> and selectively connected to the receptacle <NUM> (and thus the pin <NUM> of the connector <NUM> inserted into the receptacle <NUM>) by the multiplexer <NUM>, as described in more detail below.

Each of the circuits <NUM>-<NUM> is electrically connected to the multiplexer <NUM>, which receives a control signal from the controller <NUM>. When an optical module <NUM> is inserted into the socket <NUM>, as shown by <FIG>, the multiplexer <NUM> selectively couples one of the circuits <NUM>-<NUM> to the receptacle <NUM> based on the control signal from the controller <NUM>. As described above, at the time that the optical module <NUM> is inserted into the socket <NUM>, the controller <NUM> should be controlling the multiplexer <NUM> such that it electrically couples the Safe Mode circuit <NUM> to the receptacle <NUM> and electrically isolates the Mode A circuit <NUM> and the Mode B circuit <NUM> from the receptacle <NUM>. After detecting the presence of the optical module <NUM> in the socket <NUM>, the controller <NUM> may control the multiplexer <NUM> such that it electrically couples one of the circuits <NUM> or <NUM> to the receptacle <NUM>.

As an example, if the optical module <NUM> is of a type corresponding to the Mode A circuit <NUM>, the controller <NUM> may control the multiplexer <NUM> such that it electrically couples the Mode A circuit <NUM> to the receptacle <NUM> and electrically isolates the Mode B circuit <NUM> and the Safe Mode circuit <NUM> from the receptacle <NUM>. If the optical module <NUM> is instead of a type that corresponds to the Mode B circuit <NUM>, then the multiplexer <NUM> may be controlled to electrically couple the Mode B circuit <NUM> to the receptacle <NUM> and electrically isolate the Mode A circuit <NUM> and the Safe Mode circuit <NUM> from the receptacle <NUM>. Thus, the circuit <NUM> or <NUM> electrically and operationally compatible with the optical module <NUM> should be electrically connected to the receptacle <NUM> once the optical module <NUM> is mated with the socket <NUM> and detected by the controller <NUM>.

Note that the configuration of the adapter circuitry <NUM> connected to the pin <NUM> may be more complex than the exemplary circuitry shown by <FIG>. As an example, it is possible for the circuits <NUM>-<NUM> and the multiplexer <NUM> to share electrical components and devices as may be desired. Regardless of the actual configuration of the circuits <NUM>-<NUM>, when the controller <NUM> detects an optical module <NUM> of a certain type in the socket <NUM>, the controller <NUM> controls the multiplexer <NUM> and possibly other components and devices of the adapter circuitry <NUM> connected to a receptacle <NUM> such that the adapter circuitry is compatible with the operational and electrical requirements for the pin <NUM> inserted into that receptacle <NUM>, as specified by the applicable specifications for the type of optical module <NUM> inserted into the socket <NUM>.

In some embodiments, to meet the electrical and operational requirements of different types of optical modules <NUM>, it may be desirable for the adapter <NUM> to provide a low resistance connection to ground for a particular pin <NUM> of the module's connector <NUM> if a first type of optical module <NUM> is inserted into the socket <NUM> but to carry and process a control signal if a second type of optical module <NUM> is inserted into the socket <NUM>. As an example, when the first type of optical module <NUM> is in the socket <NUM>, the optical module <NUM> may connect the pin <NUM> to the ground plane of the module <NUM> such that the ground plane of the module <NUM> and the ground plane of the adapter <NUM> are electrically connected to each other through the pin <NUM> and the corresponding receptacle <NUM>. It is generally desirable for these two ground planes, or their functionally equivalent ground networks, to be at the same voltage potential and, thus, for the resistance in the path between the ground planes to be as low as possible. However, when an optical module <NUM> of the second type is instead inserted into the socket <NUM>, it may be desirable for the circuit of the adapter <NUM> connected to the corresponding pin <NUM> inserted into the same receptacle <NUM> to transmit or receive a control or data signal.

<FIG> depicts an exemplary embodiment of adapter circuitry <NUM> that may be used to achieve the functionality described above. In this regard, the adapter <NUM> comprises a circuit <NUM> that is electrically connected through a resistor <NUM> to a receptacle <NUM> for a particular pin position of the connector <NUM> of an optical module <NUM> mated with the socket <NUM>. The node <NUM> between the resistor <NUM> and the receptacle <NUM> is connected to ground <NUM> of the adapter <NUM> through a field-effect transistor <NUM>. When an optical module <NUM> of a first type (e.g., a Multi-PON module) is mated with the socket <NUM>, a control signal may be communicated between the circuit <NUM> and optical module <NUM> through the receptacle <NUM> and pin <NUM> (not shown in <FIG>) inserted into the receptacle <NUM>. However, when an optical module <NUM> of a second type (e.g., GPON or XGS-PON module) is inserted into the socket <NUM>, the receptacle <NUM> may be electrically connected to ground <NUM>. In the embodiment shown by <FIG>, the field-effect transistor <NUM> may be used to control in which mode the adapter <NUM> operates for the receptacle <NUM>.

In this regard, the gate of the field-effect transistor <NUM> may be electrically connected to the controller <NUM> and receive a control signal from the controller <NUM> for controlling whether the field-effect transistor <NUM> is turned on. As an example, if the controller <NUM> determines that an optical module <NUM> of the first type (e.g., a Multi-PON module) is mated with the socket <NUM>, the controller <NUM> may be configured to turn off the field-effect transistor <NUM> such that the field-effect transistor <NUM> electrically isolates ground <NUM> from the node <NUM> and thus the receptacle <NUM>, thereby enabling the circuit <NUM> to communicate with the optical module <NUM> through the receptacle <NUM>. However, if the controller <NUM> determines that an optical module <NUM> of the second type (e.g., a GPON or XGS-PON module) is mated with the socket <NUM>, the controller <NUM> may be configured to turn on the field-effect transistor <NUM> such that the field-effect transistor <NUM> electrically connects ground <NUM> to the node <NUM> and thus the receptacle <NUM>.

In safe mode, the controller <NUM> may be configured to turn off the field-effect transistor <NUM> such that the field-effect transistor <NUM> electrically isolates ground <NUM> from the node <NUM>.

In another embodiment, the field-effect transistor <NUM> may be used to switch a control signal. In this case, the resistor <NUM> acts as a pull-up resistor, the circuit <NUM> is simply a connection to the proper power supply voltage, and the field-effect transistor <NUM> acts as an inverting buffer. In this regard, a logical high signal from the controller <NUM> applied to the gate of the field-effect transistor <NUM> turns on the field-effect transistor <NUM> and pulls node <NUM> to a logical low level (e.g., ground). Conversely, a logical low signal from the controller <NUM> applied to the gate of field-effect transistor <NUM> turns off field-effect transistor <NUM> and node <NUM> is pulled-up to a logical high level (e.g., the power supply voltage) by resistor <NUM>. The field-effect transistor <NUM> must turn on and off sufficiently fast to meet the electrical specifications of the optical module <NUM>.

Also, this embodiment may implement a level-shifter function, where the power supply voltage provided by circuit <NUM> through resistor <NUM> is electrically compatible with the optical module <NUM>. In this regard, the controller <NUM> (<FIG>) may be configured to control the adapter <NUM> such that a data signal (e.g., a signal modulated with data that transitions between a logical low value and logical high value in order to convey binary data values) is received by the gate of the field-effect transistor <NUM>. When the data signal is at a logical high value, the field-effect transistor <NUM> is turned on such that the node <NUM> and, thus, receptacle <NUM> are electrically connected to ground <NUM> through the field-effect transistor <NUM>, thereby providing a logical low signal for the optical module <NUM>. When the data signal is at a logical low value, the field-effect transistor <NUM> is turned off such that the node <NUM> and, thus, receptacle <NUM> are electrically isolated from ground <NUM> by the field-effect transistor <NUM>. In such case, the signal transmitted by the circuit <NUM> passes through the receptacle <NUM> to the optical module <NUM> mated with the socket <NUM>, and such signal may have a voltage and current compatible with the optical module <NUM>. Notably, the voltage and/or current of the signal transmitted by the circuit <NUM> through resistor <NUM> may be different than the voltage and current of the data signal received by the gate of the field-effect transistor <NUM>. Thus, the circuit shown by <FIG> may perform a level-shifter function where the voltage or current of the data signal is effectively shifted to a different level that is compatible with the specifications of the optical module <NUM>.

In another embodiment, when an optical module <NUM> of a certain type (e.g., a Multi-PON module) is mated with the socket <NUM>, a control signal may be communicated from the optical module <NUM> through the receptacle <NUM> and through the resistor <NUM> to the circuit <NUM>. In this regard, the field-effect transistor <NUM> may be controlled to be off, thus electrically isolating ground <NUM> from the node <NUM> and thus the receptacle <NUM>, thereby enabling the optical module <NUM> to communicate with the circuit <NUM>. In this embodiment, the resistor <NUM> may be about zero ohms, though other resistance values are possible.

In some embodiments, the field-effect transistor <NUM> preferably has a low on-resistance and capacitance. As an example, the transistor's on-resistance, Qgs (i.e., the gate to source charge required to turn on the field-effect transistor <NUM>) and Coss (i.e., the drain output capacitance) may be less than <NUM> Ohm, <NUM> Nano Coulombs and <NUM> Pico Farads, respectively. In one embodiment, the field-effect transistor <NUM> may be a DMG2302 N-channel enhancement mode MOSFET sold by Diodes, Inc. having an on-resistance of about <NUM> Ohm, a Qgs of about <NUM> Nano Coulombs and a Coss of about <NUM> Pico Farads, though other field-effect transistors may be used in other embodiments. The field-effect transistor <NUM> provides very low on-resistance for coupling together the ground planes of adapter <NUM> and the optical module <NUM> for at least one operational mode, low Qgs for fast switching when used as an inverting buffer for accommodating a control signal communicated by the circuit <NUM> for at least one other operational mode, and low Coss capacitive loading of node <NUM> for fast switching by circuit <NUM> for at least one other operational mode.

In other embodiments, other circuit configurations may be used to achieve similar functionality. As an example, it is possible to replace the field-effect transistor <NUM> of <FIG> with a single-pole, single-throw (SPST), radio-frequency (RF) relay (not shown) to provide a low resistance connection to ground. However, such a relay may have greater cost, greater size and inferior switching performance relative to the field-effect transistor <NUM>. Yet other circuit configurations are possible in other embodiments.

In some embodiments, it is possible for the circuit <NUM> to process a high-speed data signal (e.g., greater than about <NUM> Megabits per second (Mbps)) that is transmitted to or received from an optical module <NUM> through the receptacle <NUM> for a given pin position. However, use of a field-effect transistor (FET), such as the field-effect transistor <NUM> shown by <FIG>, would likely impair the data signal at such a high rate of speed. Also, use of a series resistor, such as resistor <NUM> shown in <FIG>, would likely impair the data signal also. Alternatively, a single-pole, double-throw (SPDT) RF relay could be used in place of the field-effect transistor <NUM> to multiplex the high-speed data signal and ground, but such a relay can be relatively large and expensive. An analog switch could be used to multiplex the high-speed data signal and ground, but such a switch undesirably has a relatively high on-resistance making it undesirable for grounding the receptacle <NUM> and thus pin <NUM>.

Another embodiment of adapter circuit <NUM> in <FIG> that is suitable for a high-speed data signal is shown in <FIG>. Circuit <NUM> is electrically connected to receptacle <NUM> through capacitor <NUM>. The use of a capacitor, such as capacitor <NUM>, is well known in the art and is selected such that it does not significantly impair the high-speed data signal. Capacitor <NUM> is often a requirement specified by some types of optical modules <NUM> to provide DC isolation between the circuit <NUM> and module <NUM>. Even when not a requirement of the optical module <NUM>, the capacitor <NUM> is useful for another type of DC isolation, as described in more detail below.

In this regard, as described above and referring to <FIG> and <FIG>, some specifications for a type of optical module <NUM> may require a pin <NUM> and, thus, the receptacle <NUM> receiving the pin <NUM> to be grounded (i.e., electrically connected to ground <NUM> of the adapter <NUM>). As an example, the specifications for a Multi-PON module <NUM> may require the pins <NUM> at two particular pin positions (e.g., "Pin <NUM>" and "Pin <NUM>") to carry high-speed data signals, and the specifications for both GPON and XGS-PON modules require the pins <NUM> at these same pin positions (i.e., "Pin <NUM>" and "Pin <NUM>") to be grounded.

However, through inspection of GPON and XGS-PON modules <NUM> in detail, it has been determined that the pins <NUM> at the aforementioned pin positions to be grounded are typically connected electrically to at least one other ground pin of the module <NUM>, as is shown by <FIG>. In this regard, the optical module <NUM> shown by <FIG> has a pair of ground pins <NUM> and <NUM> for insertion into socket receptacles <NUM> and <NUM>, respectively. The pins <NUM> and <NUM> are electrically connected to ground <NUM> of the module <NUM> and to each other by a conductive via <NUM>. In this regard, the pin <NUM> is electrically connected to a conductive finger <NUM> residing on one surface (e.g. top surface) of a printed circuit board (PCB) <NUM>, and the pin <NUM> is electrically connected to a conductive finger <NUM> residing on an opposite surface (e.g., bottom surface) of the PCB <NUM>, as shown by <FIG>. Further, the pins <NUM> and <NUM> may be electrically connected to each other by the via <NUM> that extends through the PCB <NUM> from the finger <NUM> on the top surface to the finger <NUM> on the bottom surface.

Notably, as described above, the specifications for at least one module type (e.g., GPON and XGS-PON) require the pin <NUM> to be grounded, but the specifications for at least one other module type (e.g., Multi-PON) specify that the pin at this same pin-position (i.e., the pin for insertion into the receptacle <NUM>) is to carry a high-speed data signal, such as greater than <NUM> Gbps (e.g., about <NUM> Gbps).

However, it is preferable for the node <NUM> of the adapter <NUM> that is between the receptacle <NUM> and the capacitor <NUM> of the adapter <NUM> not be connected to the adapter's ground <NUM> by the methods previously described, due to impairment of the high-speed data signal or due to cost or size. Therefore, the electrical connection of the pin <NUM> of optical module <NUM> to ground <NUM> of adapter <NUM> does not pass through receptacle <NUM>, but instead passes through the ground plane of the optical module <NUM> and, in particular, through via <NUM>, pin <NUM> and receptacle <NUM>. Not having the receptacle <NUM> and thus pin <NUM> directly connected to ground <NUM> by circuit components of the adapter <NUM> generally increases the resistance between the ground planes of the adapter <NUM> and the optical module <NUM>. However, the increase in resistance is relatively small. Also, the increase in inductance between the ground planes is relatively small, since fingers <NUM> and <NUM> (<FIG>) are tightly coupled. Indeed, testing has shown that significant degradation in performance of a GPON or XGS-PON module <NUM> does not result from the circuit configuration shown by <FIG>.

In <FIG>, the circuit <NUM> may be configured to process a high-speed data signal to be transmitted to a different type of optical module <NUM>, such as a Multi-PON module for example. Such a circuit <NUM> is not operationally used when the adapter <NUM> is interfaced with the optical module <NUM> depicted by <FIG>. However, since node <NUM> is electrically connected to ground <NUM> in the module <NUM> depicted by <FIG>, care should be taken to prevent damage to the circuit <NUM> when the adapter <NUM> is mated with this type of optical module <NUM> of <FIG>. In the embodiment shown by <FIG>, the circuit <NUM> is connected to the node <NUM> through a capacitor <NUM>, which provides DC isolation between circuit <NUM> and node <NUM>, and thus the ground <NUM> of module <NUM>. Also, controller <NUM> disables the circuit <NUM> from switching when an optical module <NUM> that grounds node <NUM> is plugged in, preventing damage to circuit <NUM> due to excessive transient current flow through the capacitor <NUM> and into ground. Switching of the circuit <NUM> is also disabled by the controller <NUM> when in safe mode. As noted previously, the presence of the capacitor <NUM> should not significantly degrade the high-speed data signal communicated by the circuit <NUM> when the adapter <NUM> is interfaced with another type of optical module, such as Multi-PON. Thus, the configuration shown by <FIG> is electrically compatible with specifications for one type of optical module <NUM> specifying the pin <NUM> to be grounded and also with specifications for another type of module specifying the pin at the same pin position (i.e., the pin inserted into receptacle <NUM>) to carry a high-speed data signal.

There are various other techniques that can be used to make the adapter <NUM> electrically and operationally compatible across several different types of optical modules <NUM>. As an example, in some cases, the adapter <NUM> may implement different functions for the same pin position depending on the type of module <NUM> inserted into the socket <NUM>. In other cases, the adapter <NUM> may process a signal from a given pin position in one mode but ignore a signal from the same pin position in a different mode. As an example, in one mode of operation when an optical module <NUM> of a first type is mated with the socket <NUM>, the optical module <NUM> may transmit a data signal through a pin at a particular pin position of the connector <NUM>, and a circuit of the adapter <NUM> may process the data signal. However, in a different mode of operation when an optical module of a second type is mated with the socket <NUM>, the optical module <NUM> may transmit a control signal through a pin at the same pin position. For example, the control signal might be a "transmit fault" signal indicating whether there is a transmission fault with the optical transmitter of the transceiver <NUM>. In the safe mode, the adapter <NUM> may be controlled by the controller <NUM> such that it ignores such control signal without violating the specifications for the optical module <NUM>.

Claim 1:
An optical line terminal (<NUM>) for interfacing with any of a plurality of types of optical modules (<NUM>), wherein each of the types of optical modules corresponds to a respective optical protocol or combination of optical protocols for communicating with a plurality of optical network terminals (<NUM>) through an optical network (<NUM>), comprising:
a socket (<NUM>) for receiving an optical module (<NUM>);
optical line terminal OLT circuitry (<NUM>) configured to encapsulate first data for transmission through the optical network and to communicate with the optical network terminals for controlling upstream transmissions through the optical network by the optical network terminals, the OLT circuitry configured to transmit the first data and the first control information to a first optical module mated with the socket, the OLT circuitry configured to receive second data and second control information from the first optical module; and
a controller (<NUM>) configured to control the OLT circuitry to selectively operate in a plurality of operational modes, including at least a first operational mode and a second operational mode, the controller configured to identify a module type for the first optical module and to select one of the first operational mode and the second operational mode based on the identified module type, the controller further configured to control the OLT circuitry to operate in the selected operational mode when the first optical module is mated with the socket,
wherein the OLT circuitry is electrically and operationally compatible with a first type of optical module when operating in the first operational mode, characterized in that the first type of optical module corresponds to Multi-PON protocol, wherein the OLT circuitry is electrically and operationally compatible with a second type of optical module when operating in the second operational mode, and wherein the socket has a receptacle (<NUM>) for receiving a pin (<NUM>) of the first optical module, and wherein the controller is configured to control the OLT circuitry such that (<NUM>) the receptacle is electrically coupled to ground of the OLT circuitry when an optical module of the second type is mated with the socket and (<NUM>) the receptacle is electrically isolated from the ground of the OLT circuitry when an optical module of the first type is mated with the socket.