Monitoring and sensing in optical networks

Abstract

To provide various exemplary embodiments for supporting optical monitoring and sensing of an optical network.SOLUTION: Various example embodiments for supporting optical monitoring and sensing of an optical network are configured to support various optical network monitoring and / or sensing techniques based on the use of an optical communication device that includes a divider configured to split an optical signal into a first optical signal part and a second optical signal part, a polarization independent photodetector configured to monitor a power level of the optical signal based on the first optical signal part, and a polarization sensitive photodetector configured to monitor a polarization of the optical signal based on the second optical signal portion. Various example embodiments for supporting optical monitoring and the sensing may be configured to support the optical monitoring and the sensing in various optical networks, such as an optical access network (e.g., a passive optical network), an optical backhaul network, or the like.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] Various exemplary embodiments relate generally to optical communication systems and more particularly, but not exclusively, to supporting optical monitoring and sensing functions in optical communication systems. [Background technology]

[0002] Various communication technologies may be used to support communication for various types of communication systems. Summary of the Invention [Means for solving the problem]

[0003] In at least some exemplary embodiments, an apparatus includes an optical communication device comprising: a divider configured to divide an optical signal into a first optical signal portion and a second optical signal portion; a polarization-independent photodetector configured to monitor a power level of the optical signal based on the first optical signal portion; and a polarization-sensitive photodetector configured to monitor a polarization of the optical signal based on the second optical signal portion. In at least some exemplary embodiments, the polarization-sensitive photodetector comprises a modulator-detector configured to support modulation and detection functions. In at least some exemplary embodiments, the polarization-sensitive photodetector comprises a reverse-biased electro-absorption modulator based on the quantum-confined Stark effect (QCSE). In at least some exemplary embodiments, the polarization-sensitive photodetector comprises a polarization-sensitive interferometric modulator and a detector, wherein a first side of the polarization-sensitive interferometric modulator is connected to the divider and a second side of the polarization-sensitive interferometric modulator is connected to the detector. In at least some exemplary embodiments, the polarization-sensitive interferometric modulator comprises a Mach-Zehnder modulator or a ring modulator. In at least some exemplary embodiments, the optical communications device is configured to detect a change in polarization of the optical signal based on a determination that the power level of the first optical signal portion remains relatively constant at the polarization-independent photodetector while the absorption level of the second optical signal portion changes at the polarization-sensitive photodetector. In at least some exemplary embodiments, the optical communications device is configured to detect a condition or event associated with the optical fiber based on one of a determination that the power level of the first optical signal portion changes at the polarization-independent photodetector or a determination that the power level of the first optical signal portion remains relatively constant at the polarization-independent photodetector while the absorption level of the second optical signal portion changes at the polarization-sensitive photodetector.In at least some exemplary embodiments, the optical signal includes a back-reflected optical time domain reflectometry signal received at the optical communication device. In at least some exemplary embodiments, the optical signal includes a monitoring optical signal received at the optical communication device from a remote optical communication device via an optical fiber. In at least some exemplary embodiments, the optical signal includes a broadband sensing signal including a first wavelength and a second wavelength, the first optical signal portion being at the first wavelength and the second optical signal portion being at the second wavelength. In at least some exemplary embodiments, the optical signal includes a wavelength outside a data transmission wavelength range used for data transmission by the optical communication device, and the optical communication device is configured to support parallel operations of data transmission by the optical communication device and monitoring by the optical communication device based on the optical signal. In at least some exemplary embodiments, the optical signal includes a wavelength within a data transmission wavelength range used for data transmission by the optical communication device, and the optical communication device is configured to switch between data transmission by the optical communication device and monitoring by the optical communication device based on the optical signal. In at least some example embodiments, the divider comprises a wavelength splitter, and the optical communications device is configured to operate as both a data communications transceiver for optical data signals and an optical time domain reflectometry transceiver for optical time domain reflectometry signals, and the optical communications device further comprises a semiconductor optical amplifier disposed between the wavelength splitter and the optical fiber, the semiconductor optical amplifier configured to amplify the optical data signals and the optical time domain reflectometry signals, and a laser connected to the polarization-sensitive photodetector, the laser configured to generate light that is modulated in the polarization-sensitive photodetector for the optical data signals, and the wavelength splitter is configured to connect a first wavelength between the wavelength splitter and the polarization-independent photodetector and to connect a second wavelength, different from the first wavelength, between the wavelength splitter and the polarization-sensitive photodetector.In at least some example embodiments, the optical communications device is configured to perform the optical time domain reflectometry test by supporting initiation of an optical time domain reflectometry test by switching off the laser, ceasing modulation of the communication data by the polarization-sensitive photodetector, and modulating the semiconductor amplifier to generate optical time domain reflectometry pulses, and by supporting an optical time domain reflectometry measurement by receiving a back-reflected optical time domain reflectometry signal, detecting a reflected power of the back-reflected optical time domain reflectometry signal by the polarization-independent photodetector, and obtaining information regarding variations in polarization of the back-reflected optical time domain reflectometry signal based on detection of the at least one polarization by the polarization-sensitive photodetector. In at least some example embodiments, the optical communications device further comprises a driver configured to provide an electrical drive signal for the optical data signal, an optical time domain reflectometry electrical receiver configured to receive an electrical sense signal associated with the second optical signal portion, and an electrical circuit configured to separate the electrical drive signal for the optical data signal and the electrical sense signal associated with the second optical signal portion using at least one of time multiplexing or frequency multiplexing. In at least some example embodiments, the electrical circuit comprises an amplification path configured to connect a driver to the polarization-sensitive photodetector and a detection path configured to connect the polarization-sensitive photodetector to an optical time-domain reflectometry electrical receiver, the driver including a time switch configured to switch the electrical circuit between using the amplification path and the detection path.In at least some example embodiments, the optical communication device is configured to support continuous use of optical data communication and optical detection based on continuous modulation of communication data by a polarization-sensitive photodetector based on continuous emission of optical power by a laser associated with the polarization-sensitive photodetector to form an optical data signal, continuous detection of the received optical data signal by a polarization-independent photodetector, modulation of a first optical amplifier to generate an optical time domain reflectometry signal, continuous driving of a second optical amplifier by a DC driver to amplify the optical data signal and the optical time domain reflectometry signal, detection of the received optical data signal and a back-reflected optical time domain reflectometry signal by the polarization-independent photodetector, and detection of the back-reflected optical time domain reflectometry signal by an optical time domain reflectometry electrical receiver based on absorption of the back-reflected optical time domain reflectometry signal by the polarization-sensitive photodetector via a low frequency path of an electrical circuit. In at least some exemplary embodiments, the optical communications device includes an optical amplifier pair including a first optical amplifier configured to generate an optical time domain reflectometry signal modulated and transmitted by the optical communications device and a second optical amplifier configured to support sequential amplification of both an optical data signal transmitted by the optical communications device and an optical time domain reflectometry signal transmitted by the optical communications device; an optical time domain reflectometry driver configured to generate an optical time domain reflectometry drive signal for the first optical amplifier; and a DC driver configured to generate a DC drive signal for the second optical amplifier. In at least some exemplary embodiments, the optical communications device includes at least one of an optical receiver or an optical transceiver. In at least some exemplary embodiments, the apparatus includes a divider configured to separate the optical test signal from a set of optical signals including the optical data communications signal and the optical test signal; a circuit configured to convert the optical test signal to an analysis signal based on an electroabsorption-modulated laser capability; and a digital signal processor configured to determine at least one of polarization information of the optical test signal or phase information of the optical test signal based on the analysis signal.

[0004] In at least some exemplary embodiments, an apparatus includes an optical communication device comprising: means for splitting an optical signal into a first optical signal portion and a second optical signal portion; means for monitoring a power level of the optical signal based on the first optical signal portion; and means for monitoring a polarization of the optical signal based on the second optical signal portion. In at least some exemplary embodiments, the means for monitoring the power level of the optical signal based on the first optical signal portion comprises a polarization-independent photodetector, and the means for monitoring the polarization of the optical signal based on the second optical signal portion comprises a polarization-sensitive photodetector. In at least some exemplary embodiments, the means for monitoring the polarization of the optical signal based on the second optical signal portion comprises a modulator-detector configured to support modulation and detection functions. In at least some exemplary embodiments, the means for monitoring the polarization of the optical signal based on the second optical signal portion comprises a reverse-biased electro-absorption modulator based on the quantum-confined Stark effect (QCSE). In at least some exemplary embodiments, the means for monitoring the polarization of the optical signal based on the second optical signal portion comprises a polarization-sensitive interferometric modulator and a detector, where a first side of the polarization-sensitive interferometric modulator is connected to the divider and a second side of the polarization-sensitive interferometric modulator is connected to the detector. In at least some exemplary embodiments, the polarization-sensitive interferometric modulator comprises a Mach-Zehnder modulator or a ring modulator. In at least some exemplary embodiments, the optical communications device is configured to detect a change in polarization of the optical signal based on determining that a power level of the first optical signal portion remains relatively constant in the means for monitoring the power level of the optical signal, while an absorption level of the second optical signal portion changes in the means for monitoring the polarization of the optical signal.In at least some exemplary embodiments, the optical communication device is configured to detect a condition or event associated with the optical fiber based on one of determining that the power level of the first optical signal portion changes in the means for monitoring the power level of the optical signal, or determining that the power level of the first optical signal portion remains relatively constant in the means for monitoring the power level of the optical signal while the absorption level of the second optical signal portion changes in the means for monitoring the polarization of the optical signal. In at least some exemplary embodiments, the optical signal includes a back-reflected optical time-domain reflectometry signal received at the optical communication device. In at least some exemplary embodiments, the optical signal includes a monitoring optical signal received at the optical communication device from a remote optical communication device via the optical fiber. In at least some exemplary embodiments, the optical signal includes a broadband sensing signal including a first wavelength and a second wavelength, wherein the first optical signal portion is at the first wavelength and the second optical signal portion is at the second wavelength. In at least some example embodiments, the optical signal includes a wavelength outside a data transmission wavelength range used for data transmission by the optical communications device, and the optical communications device is configured to support parallel operations of data transmission by the optical communications device and monitoring by the optical communications device based on the optical signal. In at least some example embodiments, the optical signal includes a wavelength within a data transmission wavelength range used for data transmission by the optical communications device, and the optical communications device is configured to switch between data transmission by the optical communications device and monitoring by the optical communications device based on the optical signal.In at least some example embodiments, the means for splitting the optical signal into the first and second optical signal portions comprises a wavelength splitter, and the optical communications device is configured to operate as both a data communications transceiver for the optical data signal and an optical time domain reflectometry transceiver for the optical time domain reflectometry signal, and the optical communications device further comprises: means for amplifying the optical data signal and the optical time domain reflectometry signal disposed between the wavelength splitter and the optical fiber; and means for generating light for the optical data signal, connected to the means for monitoring the polarization of the optical signal, that is modulated in the means for monitoring the polarization of the optical signal; and the wavelength splitter is configured to connect a first wavelength between the wavelength splitter and the means for monitoring the power of the optical signal and to connect a second wavelength, different from the first wavelength, between the wavelength splitter and the means for monitoring the polarization of the optical signal. In at least some exemplary embodiments, the optical communications device is configured to support initiation of an optical time domain reflectometry test by means for switching off the means for generating light, by means for stopping modulation of communication data by the means for monitoring polarization of the optical signal, and by means for modulating the means for amplifying to generate optical time domain reflectometry pulses, and to perform an optical time domain reflectometry test by means for supporting an optical time domain reflectometry measurement by detecting the reflected power of the back-reflected optical time domain reflectometry signal by the means for receiving the back-reflected optical time domain reflectometry signal and monitoring the power of the optical signal, and obtaining information regarding variations in polarization of the back-reflected optical time domain reflectometry signal based on detection of the at least one polarization by the means for monitoring polarization of the optical signal. In at least some exemplary embodiments, the optical communications device further comprises means for providing an electrical drive signal for the optical data signal, means for receiving an electrical sense signal associated with the second optical signal portion, and means for separating the electrical drive signal for the optical data signal and the electrical sense signal associated with the second optical signal portion using at least one of time multiplexing or frequency multiplexing.In at least some example embodiments, the means for separating the electrical drive signal for the optical data signal and the electrical detection signal associated with the second optical signal portion comprises an amplification path for connecting the means for providing the electrical drive signal to the means for monitoring polarization of the optical signal and a detection path for connecting the means for monitoring polarization of the optical signal to the means for receiving the electrical detection signal, and the means for providing the electrical drive signal includes means for switching the means for separating between using the amplification path and using the detection path. In at least some example embodiments, the optical communications device is configured to support continuous use of optical data communications and optical sensing based on continuous modulation of communication data by the means for monitoring polarization of the optical signal based on continuous emission of optical power by a laser associated with the means for monitoring polarization of the optical signal to form an optical data signal, continuous detection of the received optical data signal by the means for monitoring the power of the optical signal, modulation of a first optical amplifier to generate an optical time domain reflectometry signal, continuous driving of a second optical amplifier by a DC driver to amplify the optical data signal and the optical time domain reflectometry signal, detection of the received optical data signal and a back-reflected optical time domain reflectometry signal by the means for monitoring polarization of the optical signal, and detection of the back-reflected optical time domain reflectometry signal via a low frequency path of an electrical circuit by an optical time domain reflectometry electrical receiver based on absorption of the back-reflected optical time domain reflectometry signal by the means for monitoring polarization of the optical signal.In at least some exemplary embodiments, the optical communications device includes an optical amplifier pair including a first optical amplifier configured to be modulated to generate an optical time domain reflectometry signal transmitted by the optical communications device and a second optical amplifier configured to support sequential amplification of both an optical data signal transmitted by the optical communications device and an optical time domain reflectometry signal transmitted by the optical communications device; an optical time domain reflectometry driver configured to generate an optical time domain reflectometry drive signal for the first optical amplifier; and a DC driver configured to generate a DC drive signal for the second optical amplifier. In at least some exemplary embodiments, the optical communications device includes at least one of an optical receiver or an optical transceiver. In at least some exemplary embodiments, the apparatus includes means for isolating an optical test signal from a set of optical signals including the optical data communications signal and the optical test signal, means for converting the optical test signal to an analysis signal based on an electroabsorption-modulated laser capability, and means for determining at least one of polarization information of the optical test signal or phase information of the optical test signal based on the analysis signal.

[0005] The teachings herein can be readily understood by considering the following detailed description in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a diagram of an example embodiment of a passive optical network (PON) including an optical line terminal (OLT) and a set of optical network units (ONUs) configured to support various optical monitoring and sensing functions. [Figure 2] 1A-1C are diagrams of example embodiments of optical communication devices configured to support various optical monitoring and sensing functions in various contexts based on the use of polarization-independent and polarization-sensitive photodetectors. [Figure 3]FIG. 1 is a diagram of an example embodiment of an optical communication device including an optical transceiver configured to operate as a polarization-sensitive OTDR receiver, in which the polarization-sensitive photodetector includes an electro-absorption modulator (EAM). [Figure 4] FIG. 1 is a diagram of an example embodiment of an optical communication device including an optical transceiver configured to operate as a polarization-sensitive OTDR transceiver, in which the polarization-sensitive photodetector includes an electro-absorption modulator (EAM). [Figure 5] 5 is a diagram of an example embodiment of an electronic circuit configured to support separation of a modulated optical data signal and a detected back-reflection sensing signal in the EAM of the optical transceiver of FIGS. 3 and 4. FIG. [Figure 6] FIG. 1 is a diagram of an example embodiment of an optical communication device including an optical transceiver based on a dual-section amplifier and including electronic circuitry configured to support separation of a modulated optical data signal and a detected back-reflection sensing signal. [Figure 7] FIG. 1 is a diagram of an example embodiment of an optical communication device including an optical transceiver based on a dual-section amplifier and including dedicated components configured to support separation of a modulated optical data signal and a detected back-reflection sensing signal. [Figure 8] FIG. 1 is a diagram of an example embodiment of a method for use by an optical communication device to support optical monitoring for monitoring the power and polarization of an optical signal. [Figure 9] FIG. 1 is a diagram of an example embodiment of an optical communication device including an optical transceiver configured to support optical power, polarization, and phase monitoring, where the optical polarization and phase monitoring is based on electrical multiplexing of a detection signal and subsequent processing of the mixed signal in the electrical domain. [Figure 10]FIG. 1 is a diagram of an example embodiment of an optical communication device including an optical transceiver configured to support optical power, polarization, and phase monitoring, where the optical polarization and phase monitoring is based on electrical multiplexing of a detection signal and subsequent processing of the mixed signal in the electrical domain. [Figure 11] FIG. 1 is a diagram of an example embodiment of an optical communication device including an optical transceiver configured to support optical power, polarization, and phase monitoring, where the optical polarization and phase monitoring is based on optical multiplexing of a detection signal followed by processing of the mixed signal in the electrical domain. [Figure 12] FIG. 1 is a diagram of an example embodiment of an optical communication device including an optical transceiver configured to support optical power, polarization, and phase monitoring, where the optical polarization and phase monitoring is based on optical multiplexing of a detection signal followed by processing of the mixed signal in the electrical domain. [Figure 13] FIG. 1 is a diagram of an example embodiment of an optical communication device including an optical transceiver configured to support optical power, polarization, and phase monitoring, where the optical polarization and phase monitoring is based on optical multiplexing of a detection signal followed by processing of the mixed signal in the electrical domain. [Figure 14] FIG. 1 is a diagram of an example embodiment of a method for use by an optical communication device to support optical monitoring for monitoring the polarization of an optical signal and the phase of the optical signal. [Figure 15] FIG. 1 is a diagram of an exemplary embodiment of a computer suitable for use in performing various functions presented herein. DETAILED DESCRIPTION OF THE INVENTION

[0007] To facilitate understanding, the same reference numerals have been used herein, wherever possible, to designate identical elements that are common among the various figures.

[0008] Various exemplary embodiments for supporting optical monitoring and detection of an optical network are presented. The various exemplary embodiments for supporting optical monitoring and detection of an optical network may be configured to support various optical network monitoring techniques configured to support monitoring of the optical network (e.g., to support detection, location, and / or identification of events such as fiber defects, fiber cuts, vibrations indicative of activities that may result in fiber cuts, etc.) and / or various optical network detection techniques configured to support detection on the optical network (e.g., for localized acoustic or vibration detection of conditions such as natural phenomena (e.g., earthquakes, landslides, etc.), human activity (e.g., construction activities, vibrations from railways, etc.)). The various exemplary embodiments for supporting optical monitoring and detection for optical networks may be configured to support optical monitoring and detection for optical access networks, such as passive optical networks.

[0009] Monitoring and sensing based on optical access networks, such as passive optical networks, is becoming important for a variety of reasons. For example, as optical access networks continue to be deployed, optical access network monitoring allows network operators to reduce or optimize operational costs by detecting and locating faults without dispatching a technician. For example, as optical access networks continue to be deployed, optical access network sensing provides broader geographic coverage for detecting various environmental parameters, such as natural phenomena (e.g., earthquakes, landslides, etc.), human activities (e.g., construction activities, vibrations from railways, etc.). However, optical access network monitoring and sensing is currently limited based on various aspects of the optical access network.

[0010] Optical access networks, such as passive optical networks, are typically based on direct detection (e.g., intensity modulation with direct detection (IM-DD)) rather than coherent detection because direct detection techniques are currently much more cost-effective than coherent detection. However, due to their limited sensitivity to polarization and the loss of phase information when direct detection techniques are used, direct detection currently does not provide access to the entire optical field (i.e., intensity, polarization, and phase). In addition, classical optical time-domain reflectometry (OTDR) measurements typically extract only limited information (e.g., extreme cases such as large losses at connectors and fiber breaks due to the detection of large signal intensity changes) and cannot provide more nuanced information, such as the optical signal transitions before a break, for use in fault prediction or as a sensor for PONs, because such monitoring and detection typically require the extraction of polarization and / or phase information in addition to intensity information.

[0011] Various exemplary embodiments for supporting optical monitoring and detection in a direct detection-based optical access network (e.g., an IM-DD PON) can be configured to support relatively low-cost optical monitoring and detection based on the extraction of entire optical field information (i.e., intensity, polarization, and phase) using various components already used within an IM-DD PON transceiver (e.g., based on obtaining the polarization dependence of optical phase and optical phase based on existing optical components without requiring dedicated polarization components, although it should be understood that such components may be included for various purposes). Various exemplary embodiments can be configured to support optical monitoring and detection in a DD-based PON based on optical transceivers that are sensitive to both the total power and the polarization of the optical signal, without the need to use dedicated polarization components (e.g., polarization splitters and polarization rotators) or coherent receivers, which are generally complex and expensive, thereby enabling cost-effective monitoring and detection in a DD-based PON with more information than a conventional OTDR and with less complexity than optical transceivers employing polarization components or coherent receivers. Various exemplary embodiments can be configured to take advantage of the diversity of individual functions available within existing and expected future optical transceiver designs to reuse functions as sensing elements, including polarization-independent sensing elements for monitoring power levels and polarization-sensitive sensing elements for monitoring polarization, thereby enabling the optical transceiver to be used to monitor aspects of the entire optical field (i.e., intensity, polarization, and phase) to provide improved optical monitoring and sensing capabilities. These and various other exemplary embodiments for supporting optical network monitoring and sensing will be further understood by reference to FIG. 1, which illustrates an exemplary embodiment that is a PON configured to support the various optical monitoring and sensing techniques presented herein.

[0012] FIG. 1 illustrates an example embodiment of a passive optical network (PON) that includes an optical line terminal (OLT) and a set of optical network units (ONUs) configured to support various optical monitoring and sensing functions.

[0013] The PON 100 may be configured to provide network access to a set of customers based on optical communications in various contexts and based on various technologies. For example, the PON 100 may operate as a point-to-multipoint (P2MP) data distribution system configured to provide broadband network access through the “last mile” for the customer (e.g., the final portion of the telecommunications network supporting communications for the customer, including delivering communications to and supporting communications from the customer). For example, the PON 100 may operate using various types of PON technologies and various PON standards (e.g., the G.9804 standard for 50G PON). For example, the PON 100 may be based on direct detection (e.g., based on intensity modulation with direct detection (IM-DD) or other suitable types of direct detection techniques). It should be appreciated that the PON 100 may be used in various other contexts and configured based on various other PON technologies and / or PON standards, etc., as well as various combinations thereof.

[0014] The PON 100 may include various communication elements configured to support optical communications. The PON 100 includes an optical line terminal (OLT) 110 and a set of optical network units (ONUs) 120-1-120-N (collectively, ONUs 120) connected via an optical distribution network (ODN) 130. The PON 100 may be configured to support downstream (DS) communications from the OLT 110 to the ONUs 120 via the ODN 130, and upstream (US) communications from the ONUs 120 to the OLT 110 via the ODN 130. The PON 100 may provide various combinations of wavelengths and polarizations, based on the application of dual polarizations to one or more wavelengths, as described further below. It should be understood that the PON 100 may include various other elements (omitted for clarity).

[0015] The OLT 110 is configured to support communications between the ONUs 120 and one or more upstream networks (omitted for clarity). The OLT 110 may be located at a central location, such as a central office (CO) or other suitable location. For example, the one or more upstream networks may include one or more core communications networks configured to support communications for the OLT 110 and, therefore, the ONUs 120. For example, the one or more upstream networks may include the Internet, a data center network, an enterprise network, etc., as well as various combinations thereof. For example, the OLT 110 may be configured to forward data received from one or more upstream networks downstream toward the ONUs 120 via the ODN 130 and forward data received from the ONUs 120 via the ODN 130 upstream toward one or more upstream networks. The OLT 110 includes an optical communications device 111 configured to support DS communications to the ONUs 120 and US communications from the ONUs 120. For example, the optical communications device 111 may include an optical transceiver, an optical transmitter, an optical receiver, etc., as well as various combinations thereof. Optical communications device 111 includes optical monitoring and sensing device 112 (depicted as a standalone element, but which may be integrated in whole or at least in part with optical communications device 111, with or without reusing some or all of the elements of optical communications device 111) configured to support various optical monitoring and sensing techniques as presented herein. It should be appreciated that OLT 110 may include various other elements configured to support optical communications within PON 100.

[0016] Each ONU 120 is configured to support communications between the OLT 110 and one or more downstream networks or devices (omitted for clarity). The ONUs 120 may be located within respective user premises or other suitable locations. For example, the one or more downstream networks or devices for the ONUs 120 may include one or more customer local area networks (LANs), one or more customer communication devices (e.g., modems, routers, switches, set-top boxes, smart televisions, gaming systems, computers, smartphones, etc., as well as various combinations thereof). For example, the ONUs 120 may be configured to forward data received from the OLT 110 via the ODN 130 downstream toward one or more downstream networks or devices, and to forward data received from the one or more downstream networks or devices upstream toward the OLT 110 via the ODN 130. ONUs 120-1-120-N each include a set of optical communication devices 121-1-121-N (collectively, optical communication devices 121) configured to support DS communications from OLT 110 and US communications to OLT 110. ONUs 120-1-120-N each include a set of optical monitoring and sensing devices 122-1-122-N (collectively, optical monitoring and sensing devices 122, which are depicted as standalone elements but may be integrated in whole or at least in part with optical communication device 111, with or without reusing some or all of the elements of optical communication device 111) configured to support various optical monitoring and sensing techniques as presented herein. It should be understood that ONU 120 may include various other elements configured to support optical communications within PON 100.

[0017] The ODN 130 may be a data distribution system configured to support communications between the OLT 110 and the ONUs 120, including DS communications from the OLT 110 to the ONUs 120 and US communications from the ONUs 120 to the OLT 110. For simplicity, the ODN 130 is depicted simply as an optical fiber or set of optical fibers configured to support the propagation of optical signals downstream from the OLT 110 to the ONUs 120 and upstream from the ONUs 120 to the OLT 110; however, it should be understood that the ODN 130 may be implemented using a variety of different components that may be arranged in a variety of different configurations. For example, the ODN 130 may include various passive optical components (e.g., optical fibers, optical couplers, optical splitters, etc.) that do not require power to distribute data signals between the OLT 110 and the ONUs 120. For example, the ODN 130 may be implemented using a branching configuration or other suitable P2MP configuration. It should be appreciated that ODN 130 may include various other elements to support communications between OLT 110 and ONU 120 .

[0018] Although presented herein primarily in the context of PON 100 of FIG. 1, it should be understood that the various example embodiments of the optical monitoring and detection functions presented herein may be provided in the context of various other types of optical communication networks or optical communications.

[0019] Various example embodiments of optical communication devices presented herein can be configured to support polarization monitoring in addition to power monitoring. It should be understood that at least some such example embodiments for supporting polarization monitoring in addition to power monitoring in optical communication devices are presented with respect to Figures 2-8.

[0020] FIG. 2 illustrates an example embodiment of an optical communication device configured to support various optical monitoring and sensing functions in various contexts based on the use of polarization-independent and polarization-sensitive photodetectors.

[0021] The optical communication device 200 includes a divider 210, a polarization-independent photodetector 220, and a polarization-sensitive photodetector 230. The divider 210 is configured to receive an optical signal 201 (e.g., a back-reflected OTDR signal reflected back to the optical communication device 200 if the optical communication device 200 performs optical monitoring or detection based on an OTDR-based optical signal, a remote optical monitoring signal received at the optical communication device 200 from a remote optical communication device if the optical communication device 200 performs optical monitoring or detection based on a remotely received optical signal, etc.) and to split the optical signal 201 received by the divider 210 into a first optical signal portion 212 provided to the polarization-independent photodetector 220 and a second optical signal portion 213 provided to the polarization-sensitive photodetector 230. The polarization-independent photodetector 220 is configured to monitor the power level of the optical signal 201 based on the first optical signal portion 212 (e.g., based on monitoring the power level of the first optical signal portion 212). Polarization-sensitive photodetector 230 is configured to monitor the polarization of optical signal 201 based on second optical signal portion 213 (eg, based on monitoring the polarization of second optical signal portion 213).

[0022] Divider 210, as indicated above, is configured to receive optical signal 201 (e.g., a back-reflected OTDR signal reflected back to optical communication device 200 if optical communication device 200 performs optical monitoring or detection based on an OTDR-based optical signal, a remote optical monitoring signal received at optical communication device 200 from a remote optical communication device if optical communication device 200 performs optical monitoring or detection based on a remotely received optical signal, etc.) and split optical signal 201 received at divider 210 into a first optical signal portion 212 provided to polarization-independent photodetector 220 and a second optical signal portion 213 provided to polarization-sensitive photodetector 230. Divider 210 can be implemented in various ways, which may depend on various factors (e.g., whether optical monitoring and data communication share wavelengths, the implementation of the optical monitoring function, etc.). For example, divider 210 may be an optical splitter, a wavelength-selective optical splitter, a duplexer, a triplexer, etc. It should be appreciated that divider 210 may be implemented in other ways.

[0023] Polarization-independent photodetector 220 is configured to monitor the power level of optical signal 201 based on first optical signal portion 212 received from divider 210 (e.g., based on monitoring the power level of first optical signal portion 212), as indicated above. Polarization-independent photodetector 220 may be implemented in a variety of ways. For example, polarization-independent photodetector 220 may be implemented as a PIN photodiode, a phototransistor, or any other suitable type of polarization-independent photodetector element. It should be appreciated that polarization-independent photodetector 220 may be implemented in a variety of other ways.

[0024] Polarization-sensitive photodetector 230 is configured to monitor the polarization of optical signal 201 based on second optical signal portion 213 received from divider 210 (e.g., based on monitoring the polarization of second optical signal portion 213), as indicated above. Polarization-sensitive photodetector 230 may be implemented in various ways, as discussed further below. For example, as further shown in FIG. 2, polarization-sensitive photodetector 230 may be implemented as a modulator-detector 231 configured to support modulation function 232 and detection function 233. Modulator-detector 231 may be implemented using a single component to provide modulation function 232 and detection function 233, or may be implemented using multiple components to provide modulation function 232 and detection function 233 (e.g., a modulator component configured to provide modulation function 232 and a detector component configured to provide detection function 233). For example, modulator-detector 231 may be implemented using a single component configured to support modulation function 232 and detection function 233 (e.g., a reverse-biased electroabsorption modulator (EAM) based on the quantum-confined Stark effect (QCSE), or other component configured to support modulation and detection capabilities). For example, modulator-detector 231 can be implemented using multiple components, such as using a modulator (e.g., a polarization-sensitive interferometric modulator such as a Mach-Zehnder modulator, a ring modulator, etc.) to provide modulation function 232 and a detector (e.g., a photodiode or other detector) to provide detection function 233. It should be understood that polarization-sensitive photodetector 230 may be implemented in a variety of other ways.

[0025] As indicated above, optical communication device 200 is configured to support various optical monitoring and detection functions based on monitoring optical signal 201. Optical communication device 200 may be configured to detect a change in the power level of optical signal 201 based on determining that the power level of first optical signal portion 212 changes at polarization-independent photodetector 220. Optical communication device 200 may be configured to detect a change in the polarization of optical signal 201 based on determining that the power level of first optical signal portion 212 remains relatively constant at polarization-independent photodetector 220, while the absorption level of polarization-sensitive photodetector 230 changes for second optical signal portion 213. For example, the determination of whether the power level remains "relatively constant" in polarization-independent photodetector 220 may be based on a measure of the percentage variation of power with respect to changes in polarization, and the percentage used as the threshold may be different in different contexts (e.g., less than 30% power with respect to changes in polarization is considered relatively constant, less than 20% power with respect to changes in polarization is considered relatively constant, etc.). For example, the determination of whether the absorption level of polarization-sensitive photodetector 230 "changes" may be based on a factor of variation with respect to changes in polarization, and the factor used as the threshold may be different in different contexts (e.g., a variation of at least a factor of 5, a variation of at least a factor of 10, etc.). It should be noted that the characteristics of first optical signal portion 212 at polarization-independent photodetector 220 and the characteristics of second optical signal portion 213 at polarization-sensitive photodetector 230 are used as proxies for monitoring the power and polarization characteristics of optical signal 201, and thus may be used to identify various conditions or events associated with the optical fiber through which optical signal 201 is propagating. It should be appreciated that optical communication device 200 may be configured to support various other optical monitoring and / or sensing functions for detecting various other conditions and / or events associated with the optical fiber.

[0026] The optical communication device 200 may be configured to detect a condition associated with the optical fiber (e.g., a kink in the optical fiber prior to an optical fiber break, an optical fiber break, etc.) or an event related to the optical fiber (e.g., an earthquake, a landslide, construction activity, etc.) for the optical fiber through which the optical signal 201 is received. For example, a major degradation of service on the optical fiber may be detected based on a determination that the power level of the optical signal 201 changes (e.g., based on a determination that the power level of the first optical signal portion 212 changes at the polarization-independent photodetector 220). For example, a potential degradation of service on the optical fiber (e.g., a polarization effect due to a kink in the optical fiber prior to an optical fiber break) may be detected based on a determination that the polarization of the optical signal 201 changes (e.g., based on a determination that the absorption level of the second optical signal portion 213 changes at the polarization-sensitive photodetector 230) while the power level of the optical signal 201 remains relatively constant (e.g., based on a determination that the power level of the first optical signal portion 212 remains relatively constant at the polarization-independent photodetector 220). It should be appreciated that monitoring the power and / or polarization of optical signal 201 may also be employed to use the optical fiber as a sensor for detecting various events (e.g., earthquakes, landslides, construction, etc.) It should be appreciated that optical communication device 200 may be configured to support various other optical monitoring and / or sensing functions for detecting various other conditions and / or events associated with the optical fiber.

[0027] The optical communication device 200 may be implemented in various ways as an optical communication node (e.g., an OLT or ONU in a PON, or other optical communication node in various other optical communication networks or optical communication contexts) or as part of an optical communication node (e.g., an OLT or ONU in a PON, or other optical communication node in various other optical communication networks or optical communication contexts). For example, when the optical communication device 200 is implemented as part of an optical communication node, the optical communication device 200 may be implemented as an optical receiver or part of an optical receiver (e.g., an OTDR receiver, a combination of a data receiver and an OTDR receiver, etc.), an optical transceiver or part of an optical transceiver (e.g., an OTDR transceiver, a combination of a data transceiver and an OTDR transceiver, etc.), etc. For example, depending on the implementation of the optical communication device 200, the divider 210 may be an optical splitter, a wavelength-selective optical splitter, a duplexer, a triplexer, etc. For example, depending on the implementation of optical communication device 200, polarization-independent photodetector 220 may be a PIN photodiode or other suitable type of polarization-independent photodetector element. For example, depending on the implementation of optical communication device 200, polarization-sensitive photodetector 230 may be a reverse-biased EAM based on a QCSE or other suitable type of polarization-sensitive photodetector element. It should be appreciated that optical communication device 200 may be implemented as an optical communication node or as part of an optical communication node in a variety of other ways.

[0028] It should be appreciated that optical communication device 200 may be integrated with various optical nodes in various ways to support various optical monitoring and sensing functions as presented herein.

[0029] FIG. 3 illustrates an example embodiment of an optical communication device including an optical transceiver configured to operate as a polarization-sensitive OTDR receiver, in which the polarization-sensitive photodetector includes an EAM.

[0030] The optical communication device 300 includes an optical transceiver 301 and represents the integration of the optical communication device 200 of FIG. 2 into an optical transceiver. The optical transceiver 301 is configured to support optical data communication and OTDR measurement (e.g., to monitor power and polarization), and may be configured to support the optical data communication and OTDR measurement simultaneously (e.g., using a dedicated wavelength for the OTDR measurement outside the range of wavelengths used for the optical data communication) or separately (e.g., by switching between the optical data communication and the OTDR measurement based on time division multiplexing between the optical data communication and the OTDR measurement). The optical transceiver 301 includes an optical fiber 302, a distributed feedback (DFB) laser 310, an electro-absorption modulator (EAM) 320, a PIN photodetector 330, and a duplexer 340. Because an external OTDR source, rather than the optical transceiver 301, is used to generate the OTDR signal that is sent to the optical fiber 302 to trigger the creation of the back-reflected OTDR signal, the optical transceiver 301 can be considered to operate as a polarization-sensitive OTDR receiver.

[0031] Optical transceiver 301 is configured to support the transmission of optical data signals to and reception of optical data signals from remote optical nodes during optical data communications. Optical transceiver 301 is configured to transmit data to remote optical nodes using DFB laser 310, EAM 320, and duplexer 340, e.g., DFB laser 310 provides an optical signal, EAM 320 modulates data onto the optical signal to form an optical data signal, and duplexer 340 directs the optical data signal onto optical fiber 302 for propagation to the remote optical node. Optical transceiver 301 is configured to receive data from remote optical nodes using duplexer 340 and PIN photodetector 330, e.g., duplexer 340 receives an optical data signal on optical fiber 302 and directs the optical data signal to PIN photodetector 330 for detection of the optical data signal and recovery of data transmitted by the remote optical node. It is to be understood that optical transceiver 301 may include other elements that may be involved in supporting the communication of data by optical transceiver 301 of optical communication device 300 .

[0032] During an OTDR measurement, optical transceiver 301 transmits an OTDR signal via optical fiber 302 and receives the back-reflected OTDR signal via optical fiber 302. Duplexer 340 receives the back-reflected OTDR signal and provides a first portion of the back-reflected OTDR signal to PIN photodetector 330 and a second portion of the back-reflected OTDR signal to EAM 320. PIN photodetector 330 is sensitive to optical power, so it can monitor the power level of the back-reflected OTDR signal by monitoring the optical power of the first portion of the back-reflected OTDR signal. EAM 320 has absorption that is highly sensitive to optical polarization, so it can monitor changes in the polarization of the back-reflected OTDR signal by monitoring the optical polarization of the second portion of the back-reflected OTDR signal. Here, EAM 320, which is typically used for high-speed data modulation (as described above for optical data communications), is repurposed as a polarization-sensitive detector, thereby enabling support for polarization monitoring using existing optical transceiver components. As a result, the use of PIN photodetector 330 and EAM 320 allows for simultaneous monitoring of variations in the total power and polarization of the incoming back-reflected OTDR signal (e.g., if the total power remains constant at PIN photodetector 330 but the absorption at EAM 320 changes, this means that the polarization is changing). In this way, optical transceiver 301 can support monitoring of both the power and polarization properties of light propagating on optical fiber 302.

[0033] For OTDR measurements, the optical transceiver 301 can be configured to support the use of various types of OTDR source signals that can be utilized to trigger the creation of a back-reflected OTDR signal to support the OTDR measurement in the optical transceiver 301. For example, the OTDR signal can be a broadband detection signal (e.g., covering λ1 and λ2 within the passband filter of the duplexer 340), where (1) the signal at wavelength λ1 is detected by the polarization-independent PIN photodetector 330 (which is the receiver portion of the data transceiver), and 2) the signal at wavelength λ2 is detected by the reverse-biased EAM 320, which acts as a photodiode during the detection measurement but is polarization-independent. The external OTDR source providing the OTDR signal sent through the optical fiber 302 may be a single broadband emitter covering wavelengths λ1 and λ2, two emitters at wavelengths λ1 and λ2, or a single external emitter at one wavelength (either λ1 or λ2) where the other wavelength (the other of λ1 or λ2) is provided by a different source (e.g., a different external source or the DFB laser 310). It should be appreciated that various other types of OTDR source signals may be utilized to trigger the creation of a back-reflected OTDR signal to support OTDR measurements in the optical transceiver 301.

[0034] It should be appreciated that the optical communication device 301 may be utilized in various optical communication network contexts, such as within the PON 100 of FIG. 1 (e.g., the optical communication device 300 may be used as the optical communication device 111 within the OLT 110 or as one of the optical communication devices 121 within one of the ONUs 120). In this case, the optical transceiver 301 may be implemented as a relatively simple DD-based optical transceiver that can be used to detect polarization effects within the ODN 130 without adding optical components to the optical transceiver 301 for the purpose of supporting detection of polarization effects within the ODN 130 (e.g., based on the use of an existing EAM 320 that may already be present within the DD-based optical transceiver for modulation of data onto an optical signal for communication of the data over the optical network as a polarization-sensitive photodetector to support detection of polarization effects without the need to incorporate additional optical components within the DD-based optical transceiver).

[0035] FIG. 4 illustrates an example embodiment of an optical communication device including an optical transceiver configured to operate as a polarization-sensitive OTDR transceiver, in which the polarization-sensitive photodetector includes an EAM.

[0036] The optical communication device 400 includes an optical transceiver 401 and represents the integration of the optical communication device 200 of FIG. 2 into the optical transceiver 401. The optical transceiver 401 is configured to support optical data communication and OTDR measurement (e.g., to monitor power and polarization), and may be configured to support the optical data communication and OTDR measurement simultaneously (e.g., using a dedicated wavelength for the OTDR measurement outside the range of wavelengths used for the optical data communication) or separately (e.g., by switching between the optical data communication and the OTDR measurement based on time division multiplexing between the optical data communication and the OTDR measurement). The optical transceiver 401 includes an optical fiber 402, a DFB laser 410, an EAM 420, a PIN photodetector 430, and a duplexer 440. The optical transceiver 401 is configured to support the reuse of components (e.g., the EAM 420 and the PIN photodetector 430) for both the optical data communication and the OTDR measurement.

[0037] The optical transceiver 401 is configured to support the transmission of optical data signals to and reception of optical data signals from a remote optical node during optical data communication. The optical transceiver 401 is configured to transmit data to the remote optical node using a DFB laser 410, an EAM 420, and a duplexer 440, e.g., the DFB laser 410 provides an optical signal, the EAM 420 modulates data onto the optical signal to form an optical data signal, and the duplexer 440 directs the optical data signal onto the optical fiber 402 for propagation to the remote optical node. The optical transceiver 401 is configured to receive data from the remote optical node using the duplexer 440 and the PIN photodetector 430, e.g., the duplexer 440 receives the optical data signal on the optical fiber 402 and directs the optical data signal to the PIN photodetector 430 for detection of the optical data signal and recovery of the data transmitted by the remote optical node. It should be understood that optical transceiver 401 may include other elements that may be involved in supporting the communication of data by optical transceiver 401 of optical communication device 400 .

[0038] During an OTDR measurement, the optical transceiver 401 transmits an OTDR signal via the optical fiber 402 and receives the back-reflected OTDR signal via the optical fiber 402. The duplexer 440 receives the back-reflected OTDR signal and provides a first portion of the back-reflected OTDR signal to the PIN photodetector 430 and a second portion of the back-reflected OTDR signal to the EAM 420. The PIN photodetector 430 is sensitive to optical power, so it can monitor the power level of the back-reflected OTDR signal by monitoring the optical power of the first portion of the back-reflected OTDR signal. The EAM 420 has absorption that is highly sensitive to optical polarization, so it can monitor changes in the polarization of the back-reflected OTDR signal by monitoring the optical polarization of the second portion of the back-reflected OTDR signal. Here, the EAM 420, which is typically used for high-speed data modulation (as described above for optical data communications), is repurposed as a polarization-sensitive detector, thereby enabling support for polarization monitoring using existing optical transceiver components. As a result, the use of PIN photodetector 430 and EAM 420 allows for simultaneous monitoring of variations in the total power and polarization of the incoming back-reflected OTDR signal (e.g., if the total power remains constant at PIN photodetector 430 but the absorption at EAM 420 changes, this means that the polarization is changing). In this way, optical transceiver 401 can support monitoring of both the power and polarization properties of light propagating on optical fiber 402.

[0039] 3 (which uses an external OTDR source to generate an OTDR signal), the optical transceiver 401 is configured to generate an OTDR signal. Unlike the optical transceiver 301 of FIG. 3, the optical transceiver 401 further includes a semiconductor optical amplifier (SOA) 403 disposed between the duplexer 440 and the optical fiber 402. The SOA 403 is configured to support amplification of the optical data signal communicated by the optical transceiver 401 (e.g., as a preamplifier to provide sufficient transmit power for the optical data signal transmitted by the optical transceiver 401 via the optical fiber 402 and to provide sufficient sensitivity for the optical data signal received by the optical transceiver 401 via the optical fiber 402), as well as to operate as an OTDR signal source for generating an OTDR signal transmitted to the optical fiber 402 to trigger creation of a back-reflected OTDR signal for OTDR measurement in the optical transceiver 401. It should be appreciated that the use of SOA 402 as a broadband OTDR emitter enables operation of optical transceiver 401 as a dual-use transceiver that can function not only as a classical data transceiver, but also as an advanced OTDR sensing element.

[0040] FIG. 5 illustrates an exemplary embodiment of an electronic circuit configured to support separation of a modulated optical data signal and a detected back-reflected detection signal in an EAM of the optical transceivers of FIGS. 3 and 4 . The EAM electronic circuit 500 is configured to support separation of the modulated optical data signal and the back-reflected detection signal. The electronic circuit includes a bias Tee 510 configured to be coupled to the EAM, a driver 520 coupled to the bias Tee 510 through a high frequency (HF) path, and a biasing source and OTDR receiver 530 coupled to the bias Tee 510 through a low frequency path. The driver 520 is configured to send data to the EAM for modulation onto an optical signal (e.g., from a DFB laser associated with the EAM) through the HF path of the bias Tee 510. The biasing source and OTDR receiver 530 is configured to detect the back-reflected OTDR signal absorbed by the EAM through the LF path of the bias Tee 510 to determine whether the power level of the back-reflected OTDR signal is constant or varying. The EAM electronics 500 is configured to support separation of the modulated optical data signal and the back-reflected sense signal without degrading the HF path of the EAM electronics 500 .

[0041] Although the separation of the modulated optical data signal and the detected back-reflection detection signal in the EAM of the optical transceiver has been presented primarily with respect to exemplary embodiments in which the separation is based on the HF and LF paths of the bias Tee 510, it should be understood that in at least some exemplary embodiments, the separation of the modulated optical data signal and the detected back-reflection detection signal in the EAM of the optical transceiver may be based on the use of time switching to select either the amplification path of the modulated optical data signal or the detection path of the detected back-reflection detection signal in the EAM electronics 500 based on time division multiplexing. For example, the separation of the modulated optical data signal and the detected back-reflection detection signal in the EAM of the optical transceiver may be based on the use of time switching in the driver 510 of the electronics. For example, time division multiplexing can allocate one frame out of every 100 frames, thereby supporting use of the optical transceiver for detection every 12.5 milliseconds. It should be understood that the separation of the modulated optical data signal and the detected back-reflection detection signal in the EAM of the optical transceiver may be implemented in other ways.

[0042] FIG. 6 illustrates an example embodiment of an optical communication device including an optical transceiver based on a dual-section amplifier and including electronic circuitry configured to support separation of the modulated optical data signal and the detected back-reflection sensing signal.

[0043] The optical communication device 600 includes an optical transceiver 601 and represents the integration of the optical communication device 200 of FIG. 2 into an optical transceiver. The optical transceiver 601 is configured to support optical data communication and OTDR measurement (e.g., to monitor power and polarization), and may be configured to support the optical data communication and OTDR measurement simultaneously (e.g., using a dedicated wavelength for the OTDR measurement outside the range of wavelengths used for the optical data communication) or separately (e.g., by switching between the optical data communication and the OTDR measurement based on time division multiplexing between the optical data communication and the OTDR measurement). The optical transceiver 601 includes an optical fiber 602, a semiconductor optical amplifier (SOA) 603, a reflective SOA (RSOA) 604 (which may alternatively be an SOA), a splitter 605, a DFB laser 610, an EAM 620, a PIN photodetector 630, and a duplexer 640. The optical transceiver 601 is configured to support reuse of components (eg, the EAM 620 and the PIN photodetector 630) for both optical data communication and OTDR measurements.

[0044] Optical transceiver 601 is configured to support the transmission of optical data signals to and reception of optical data signals from remote optical nodes during optical data communications. Optical transceiver 601 is configured to transmit data to remote optical nodes using DFB laser 610, EAM 620, and duplexer 640, e.g., DFB laser 610 provides an optical signal, EAM 620 modulates data onto the optical signal to form an optical data signal, and duplexer 640 directs the optical data signal onto optical fiber 602 for propagation to the remote optical node. Optical transceiver 601 is configured to receive data from remote optical nodes using duplexer 640 and PIN photodetector 630, e.g., duplexer 640 receives an optical data signal on optical fiber 602 and directs the optical data signal to PIN photodetector 630 for detection of the optical data signal and recovery of data transmitted by the remote optical node. It should be understood that optical transceiver 601 may include other elements that may be involved in supporting the communication of data by optical transceiver 601 of optical communication device 600 .

[0045] During an OTDR measurement, the optical transceiver 601 transmits an OTDR signal via the optical fiber 602 and receives the back-reflected OTDR signal via the optical fiber 602. The duplexer 640 receives the back-reflected OTDR signal and provides a first portion of the back-reflected OTDR signal to the PIN photodetector 630 and a second portion of the back-reflected OTDR signal to the EAM 620. The PIN photodetector 630 is sensitive to optical power and can monitor the power level of the back-reflected OTDR signal by monitoring the optical power of the first portion of the back-reflected OTDR signal. The EAM 620 has absorption that is highly sensitive to optical polarization and can monitor changes in the polarization of the back-reflected OTDR signal by monitoring the optical polarization of the second portion of the back-reflected OTDR signal. Here, the EAM 620, which is typically used for high-speed data modulation (as described above for optical data communications), is repurposed as a polarization-sensitive detector, thereby enabling support for polarization monitoring using existing optical transceiver components. As a result, the use of PIN photodetector 630 and EAM 620 enables simultaneous monitoring of variations in the total power and polarization of the incoming back-reflected OTDR signal (e.g., if the total power remains constant at PIN photodetector 630 but the absorption at EAM 620 changes, this means that the polarization is changing). In this way, optical transceiver 601 can support monitoring of both the power and polarization properties of light propagating on optical fiber 602. Here, PIN photodetector 630 and EAM 620 are dual-use components used to support both data communications and OTDR measurements, eliminating the need to use an additional PIN photodetector or an additional EAM to support OTDR measurements (dedicated to supporting OTDR measurements), and further enabling support of power and polarization monitoring without the need for dedicated polarization components such as polarization splitters and rotators, or the need for a coherent receiver.

[0046] The optical transceiver 601 is configured to operate in a manner similar to the optical transceiver 401 of FIG. 4, except for the following: (1) a dual-section (R) SOA with only DC drive is used in the adjacent OTDR drive and data paths for OTDR pulse generation to avoid perturbation of the data signal by OTDR modulation (e.g., OTDR modulation of the SOA 403 in the optical transceiver 401 of FIG. 4), and (2) the detection scheme can be performed by frequency separation (e.g., a high-frequency signal for data and a DC or low-frequency signal for OTDR). Unlike the optical transceiver 401, the optical transceiver 601 includes a dual-section (R) SOA including the SOA 603 (disposed between the duplexer 640 and the optical fiber 602) and the RSOA 604 (connected in the path between the duplexer 640 and the SOA 603). The SOA 603 is driven by a DC control signal (for DC drive in the data path) and is configured to support amplification of the optical data signal communicated by the optical transceiver 601 (e.g., as a preamplifier to provide sufficient transmit power for the optical data signal transmitted by the optical transceiver 601 and sufficient sensitivity for the optical data signal received by the optical transceiver 601). The RSOA 604 is driven by an OTDR drive signal (for OTDR pulse generation) and is configured to operate as an OTDR signal source to generate an OTDR signal that is transmitted to the optical fiber 602 and triggers the creation of a back-reflected OTDR signal for OTDR measurement in the optical transceiver 601. The splitter 605 is configured to separate the signal exchanged between the SOA 603 and the duplexer 640 from the OTDR signal provided from the RSOA 604 to the SOA 603 for transmission through the optical fiber 602. Also, unlike the optical transceiver 401, the optical transceiver 601 further includes an EAM electronic circuit 500, which allows the optical transceiver 601 to support detection schemes based on frequency separation (e.g., high frequency signals for data communication, DC or low frequency signals for OTDR).

[0047] As described above, the optical transceiver 601 is configured to support optical data communication and OTDR measurements. The combination of the DFB laser 610 and the EAM 620 continuously emits data, which is sent to the EAM 620 by the driver 520 of the EAM electronics 500 through the HF path of the bias Tee 510 of the EAM electronics 500. Because the SOA 603 is continuously biased, the data flux from the EAM 620 is not perturbed by the OTDR signal generated by the RSOA 604. The biasing source and OTDR receiver 530 of the EAM electronics 500 detects back-reflected light absorbed by the EAM 620 from the OTDR back-reflected signal through the LF path of the bias Tee 510 of the EAM electronics. The PIN photodetector 630 detects both the received data signal (at wavelength λ1) to support data communication and the back-reflected OTDR signal to support OTDR measurements. It should be appreciated that the received data signal and the back-reflected OTDR signal can be separated in a variety of ways (eg, by an analog filter before processing, digitally in a DSP, etc.).

[0048] It should be appreciated that the optical communication device 600 is configured such that the EAM electronics 500 enables the optical transceiver 601 to support detection schemes based on frequency separation (e.g., high frequency signals for data communications, DC or low frequency signals for OTDR), as opposed to incorporating a separate dedicated PIN photodetector and EAM dedicated to supporting power and polarization monitoring (an example embodiment of which is presented with respect to FIG. 7).

[0049] FIG. 7 illustrates an example embodiment of an optical communication device that includes an optical transceiver that is based on a dual-section amplifier and includes dedicated components configured to support separation of the modulated optical data signal and the detected back-reflection sensing signal.

[0050] The optical communication device 700 includes an optical transceiver 701 and represents the integration of the optical communication device 200 of FIG. 2 into an optical transceiver. The optical transceiver 701 is configured to support optical data communication and OTDR measurement (e.g., to monitor power and polarization), and may be configured to support the optical data communication and OTDR measurement simultaneously (e.g., using a dedicated wavelength for the OTDR measurement outside the range of wavelengths used for the optical data communication) or separately (e.g., by switching between the optical data communication and the OTDR measurement based on time division multiplexing between the optical data communication and the OTDR measurement). The optical transceiver 701 includes an optical fiber 702, a semiconductor optical amplifier (SOA) 703, a reflective SOA (RSOA) 704 (which may alternatively be an SOA), a splitter 705, a DFB laser 710, an EAM 720, a PIN photodetector 730, a duplexer 740, a PIN photodetector 760, and an EAM 770. The optical transceiver 701 is configured to support the use of dedicated components for optical data communication (e.g., DBL 710, EAM 720, PIN photodetector 730, and duplexer 740) and for OTDR measurement (e.g., PIN photodetector 760 and EAM 770). The splitter 705 is configured to separate the optical data communication signal for optical data communication from the OTDR signal used for OTDR measurement.

[0051] The optical transceiver 701 is configured to support the transmission of optical data signals to and reception of optical data signals from a remote optical node during optical data communication. The optical transceiver 701 is configured to transmit data to the remote optical node using a DFB laser 710, an EAM 720, and a duplexer 740, e.g., the DFB laser 710 provides an optical signal, the EAM 720 modulates data onto the optical signal to form an optical data signal, and the duplexer 740 directs the optical data signal onto the optical fiber 702 for propagation to the remote optical node. The optical transceiver 701 is configured to receive data from the remote optical node using the duplexer 740 and a PIN photodetector 730, e.g., the duplexer 740 receives the optical data signal on the optical fiber 702 and directs the optical data signal to the PIN photodetector 730 for detection of the optical data signal and recovery of the data transmitted by the remote optical node. It is to be understood that optical transceiver 701 may include other elements that may be involved in supporting the communication of data by optical transceiver 701 of optical communication device 700 .

[0052] During an OTDR measurement, the optical transceiver 701 transmits an OTDR signal via an optical fiber 702 and receives a back-reflected OTDR signal via the optical fiber 702. The back-reflected OTDR signal is directed to a splitter 705. The splitter 705 receives the back-reflected OTDR signal and provides a first portion of the back-reflected OTDR signal to a PIN photodetector 760 and a second portion of the back-reflected OTDR signal to an EAM 770. The PIN photodetector 760 is sensitive to optical power and can monitor the power level of the back-reflected OTDR signal by monitoring the optical power of the first portion of the back-reflected OTDR signal. The EAM 770 has absorption that is highly sensitive to optical polarization and can monitor changes in the polarization of the back-reflected OTDR signal by monitoring the optical polarization of the second portion of the back-reflected OTDR signal. As a result, the use of PIN photodetector 760 and EAM 770 allows for simultaneous monitoring of variations in the total power and polarization of the incoming back-reflected OTDR signal (e.g., if the total power remains constant at PIN photodetector 760 but the absorption at EAM 770 changes, this means that the polarization is changing). In this way, optical transceiver 701 can support monitoring of both the power and polarization properties of light propagating on optical fiber 702. Here, PIN photodetector 760 and EAM 770 are separate components dedicated to OTDR measurements, eliminating the need to reuse PIN photodetector 730 and EAM 720 (which are dedicated to supporting data communications) to support OTDR measurements, and further allowing power and polarization monitoring to be supported without the need for dedicated polarization components such as polarization splitters and rotators, or the need for coherent receivers.

[0053] 4, except that (1) a dual-section (R) SOA with only DC drive is used in the adjacent OTDR drive and data paths for OTDR pulse generation to avoid perturbation of the data signal due to OTDR modulation (e.g., OTDR modulation of SOA 403 in optical transceiver 401 of FIG. 4), and (2) the detection scheme can be performed by using adjacent dedicated PIN photodetector and EAM elements (e.g., PIN photodetector 760 and EAM 770). Unlike optical transceiver 401, optical transceiver 701 includes a dual-section (R) SOA including a semiconductor optical amplifier (SOA) 703 disposed between duplexer 740 and optical fiber 702, and a reflective SOA (RSOA) 704 connected in the path between the duplexer and SOA 703. The SOA 703 is driven by a DC control signal (for DC drive in the data path) and is configured to support amplification of the optical data signal communicated by the optical transceiver 701 (e.g., as a preamplifier to provide sufficient transmit power for the optical data signal transmitted by the optical transceiver 701 and sufficient sensitivity for the optical data signal received by the optical transceiver 701). The RSOA 704 is driven by an OTDR drive signal (for OTDR pulse generation) and is configured to operate as an OTDR signal source to generate an OTDR signal that is transmitted to the optical fiber 702 and triggers the creation of a back-reflected OTDR signal for OTDR measurement in the optical transceiver 701. The splitter 705 is configured to separate the OTDR signal, which is the signal provided from the RSOA 604 to the SOA 603 for transmission through the optical fiber 602, from the back-reflected OTDR signal and the optical data communication signal. Furthermore, unlike optical transceiver 401, optical transceiver 701 further includes an additional PIN photodetector 760 for dedicated power monitoring in optical transceiver 701 and an additional EAM 770 for dedicated polarization monitoring in optical transceiver 701.

[0054] As described above, the optical transceiver 701 is configured to support optical data communication and OTDR measurement. The RSOA 704 can emit in a limited wavelength band (e.g., using a Bragg grating or other suitable element) to avoid crosstalk of the OTDR signal with the data signal. In this case, the SOA 703 (a DC-based SOA configured to operate as both a booster for the transmitted optical signal and a preamplifier for the received optical signal) is not modulated, and therefore the optical data communication signal is not perturbed, allowing continuous data transmission and OTDR-based detection. Additionally, because the optical transceiver 701 includes dedicated PIN photodetector and EAM elements (e.g., PIN photodetector 760 and EAM 770), the EAM 720 and PIN photodetector 730 can be dedicated to supporting data communication; these elements do not need to be disabled to measure the back-reflected light from the back-reflected OTDR signal associated with OTDR measurement.

[0055] It should be appreciated that optical communications device 700 is configured such that a separate PIN photodetector (separate from the PIN photodetector used for data communications) and a separate EAM (separate from the EAM used for data communications) are dedicated to supporting power and polarization monitoring, as opposed to incorporating EAM electronics to enable an optical transceiver to support a detection scheme based on frequency separation (an example embodiment of which is presented with respect to FIG. 6 ).

[0056] FIG. 8 illustrates an exemplary embodiment of a method for use by an optical communications device to support optical monitoring. While presented primarily sequentially, it should be understood that at least some of the functions of method 800 may occur simultaneously or in a different order than presented with respect to FIG. 8 . Method 800 begins at block 801. At block 810, a divider of the optical communications device splits an optical signal into a first optical signal portion and a second optical signal portion. At block 820, a polarization-independent photodetector of the optical communications device monitors the power level of the optical signal based on the first optical signal portion. At block 830, a polarization-sensitive photodetector of the optical communications device monitors the polarization of the optical signal based on the second optical signal portion. At block 899, method 800 ends.

[0057] It should be appreciated that various exemplary embodiments of optical communications devices configured to support polarization monitoring in addition to power monitoring (e.g., exemplary embodiments for supporting polarization monitoring in addition to power monitoring in optical communications devices, such as those presented with respect to Figures 2-8) may be provided in various other manners.

[0058] Various example embodiments of optical communication devices presented herein can be configured to support polarization and phase monitoring in addition to power monitoring. It should be understood that at least some such example embodiments for supporting polarization and phase monitoring in addition to power monitoring in optical communication devices are presented with respect to Figures 9-14.

[0059] Various exemplary embodiments for supporting polarization and phase monitoring may be based on simplified polarization and phase detection using polarization- and phase-sensitive receivers based on the use of electroabsorption modulated laser (EML) technology (e.g., one or more EMLs configured to support EML capabilities). The EML includes a distributed feedback (DFB) laser and an electroabsorption modulator (EAM), where the DFB laser is injection-locked to the input wavelength of the EML, and then the EAM section of the EML acts as a local oscillator (LO) that mixes with the downstream signal to provide a mixed signal. The mixed signal can be processed in the electrical domain (e.g., based on a detection DSP) to extract optical polarization and phase information. This scheme may be based on electrical multiplexing of the detection signals (e.g., exemplary embodiments of which are presented with respect to FIGS. 9-10) or optical multiplexing of the detection signals (e.g., exemplary embodiments of which are presented with respect to FIGS. 11-13). It should be understood that the description of the exemplary embodiments of Figures 9-13 focuses primarily on the detection scheme, and that the sensing signal used to extract the polarization and phase information may be a monitoring signal received from a remote device or a back-reflected OTDR signal that is back-reflected based on local injection of an OTDR signal (e.g., using one of various OTDR signal source configurations, such as an external OTDR signal source, an SOA placed between the divider and the optical fiber, a dual (R) SOA pair, or any other OTDR-based scheme presented with respect to the exemplary embodiments of Figures 3-8).

[0060] FIG. 9 illustrates an example embodiment of an optical communication device including an optical transceiver configured to support optical power, polarization, and phase monitoring, where the optical polarization and phase monitoring is based on electrical multiplexing of the sensed signal and subsequent processing of the mixed signal in the electrical domain.

[0061] Optical communication device 900 includes optical transceiver 901. Optical transceiver 901 is configured to support optical data communication as well as optical detection measurements (e.g., to monitor power, polarization, and phase), and may be configured to support optical data communication and optical detection measurements simultaneously (e.g., using a dedicated wavelength for the optical detection measurements outside the range of wavelengths used for optical data communication) or separately (e.g., by switching between optical data communication and optical detection measurements based on time division multiplexing between the optical data communication and the optical detection measurements). Optical transceiver 901 includes an optical fiber 902, a DFB laser 910, an EAM 920, a PIN photodetector 930, a duplexer 940, an SOA 950, a tap 951, and various additional components configured to support optical polarization and phase monitoring, such as a polarizing beam splitter (PBS) 960, a pair of EAMs 970-1 and 970-2 (collectively, EAMs 970), a pair of LO DFB lasers 980-1 and 980-2 (collectively, LO-DFB lasers 980), and a pair of filters 990-1 and 990-2 (collectively, filters 990). Optical communication device 900 further includes a sensing DSP 999 configured to support processing of the mixed signal in the electrical domain to monitor polarization and phase.

[0062] The optical transceiver 901 is configured to support transmission of optical data signals to and reception of optical data signals from a remote optical node during optical data communication. The optical transceiver 901 is configured to transmit data to the remote optical node using a DFB laser 910, an EAM 920, and a duplexer 940, e.g., the DFB laser 910 provides an optical signal, the EAM 920 modulates data onto the optical signal to form an optical data signal, and the duplexer 940 directs the optical data signal onto the optical fiber 902 for propagation to the remote optical node. Optical transceiver 901 is configured to receive data from a remote optical node using duplexer 940, SOA 950, and PIN photodetector 930, e.g., duplexer 940 receives an optical data signal on optical fiber 902, directs the optical data signal to SOA 950, which amplifies the optical data signal, and directs the amplified optical data signal to PIN photodetector 930 for detection of the optical data signal and recovery of data transmitted by the remote optical node. It should be appreciated that optical transceiver 901 may include other elements that may be involved in supporting communication of data by optical transceiver 901 of optical communication device 900.

[0063] During an optical detection measurement, the optical transceiver 901 receives an optical test signal (e.g., a monitoring signal received over the optical fiber 902 from a remote optical communication device or a back-reflected OTDR signal received over the optical fiber 902). The duplexer 940 directs the optical test signal, as well as the received optical data signal, to the PIN photodetector 930. This results in mixing of the optical data signal and the optical test signal to form a mixed signal that is provided from the duplexer to the SOA 950. The SOA 950 amplifies the mixed signal to form an amplified mixed signal and provides the amplified mixed signal to the PIN photodetector 930. A tap 951, disposed between the SOA 950 and the PIN photodetector 930, taps a small amount of optical power from the amplified mixed signal to form a detection signal and directs the detection signal to additional components configured to support optical polarization and phase monitoring. It should be noted that the detection channel may be modulated at any suitable data rate and, in at least some exemplary embodiments, may be modulated at a rate significantly lower than that of the optical data channel to enable detection solutions that support relatively low complexity and power consumption.

[0064] During optical detection measurements, the optical transceiver 901 determines optical polarization and phase information based on EML techniques. The detection signal from the tap 951 is provided to the PBS 960, which separates the orthogonal polarization states to form separated optical signals and provides the separated optical signals to the EAMs 970-1 and 970-2, respectively (e.g., a first optical signal based on a first polarization is provided to the EAM 970-1, and a second optical signal based on a second polarization is provided to the EAM 970-2). The separated optical signals are mixed with local oscillator signals provided by injection-locked low-energy distributing feedback (LO) lasers 980-1 and 980-2 associated with the EAMs 970-1 and 970-2, respectively, to provide mixed signals associated with the EAMs 970-1 and 970-2, respectively. The mixed signals from EAMs 970-1 and 970-2 are provided to filters 990-1 and 990-2, respectively, which filter the mixed signals and filter the low-frequency monitoring signals from the high-speed data signals to produce filtered signals. The filtered signals are provided from filters 990-1 and 990-2 to a detection DSP 999, which performs processing based on the filtered signals to determine optical polarization and phase information. Here, the filtered signals can be used as analysis signals that can be analyzed or otherwise processed by DSP 999 to determine polarization and / or phase information.

[0065] FIG. 10 illustrates an example embodiment of an optical communication device including an optical transceiver configured to support optical power, polarization, and phase monitoring, where the optical polarization and phase monitoring is based on electrical multiplexing of the sensed signal and subsequent processing of the mixed signal in the electrical domain.

[0066] The optical communication device 1000 includes an optical transceiver 1001. The optical transceiver 1001 is configured to support optical data communication and optical detection measurements (e.g., to monitor power, polarization, and phase), and may be configured to support the optical data communication and optical detection measurements simultaneously (e.g., using a dedicated wavelength for the optical detection measurements outside the range of wavelengths used for the optical data communication) or separately (e.g., by switching between the optical data communication and the optical detection measurements based on time division multiplexing between the optical data communication and the optical detection measurements). The optical transceiver 1001 includes an optical fiber 1002, a DFB laser 1010, an EAM 1020, a PIN photodetector 1030, a duplexer 1040, an SOA 1050, a tap 1051, and various additional components (e.g., an EAM 1070, a LO DFB laser 1080, and a filter 1090) configured to support optical polarization and phase monitoring. The optical communication device 1000 further includes a sensing DSP 1099 configured to support processing of the mixed signal in the electrical domain to monitor polarization and phase.

[0067] The optical transceiver 1001 is configured to support transmission of optical data signals to and reception of optical data signals from a remote optical node during optical data communication. The optical transceiver 1001 is configured to transmit data to the remote optical node using a DFB laser 1010, an EAM 1020, and a duplexer 1040, e.g., the DFB laser 1010 provides an optical signal, the EAM 1020 modulates data onto the optical signal to form an optical data signal, and the duplexer 1040 directs the optical data signal onto the optical fiber 1002 for propagation to the remote optical node. The optical transceiver 1001 is configured to receive data from a remote optical node using the duplexer 1040, the SOA 1050, and the PIN photodetector 1030, e.g., the duplexer 1040 receives an optical data signal on the optical fiber 1002, directs the optical data signal to the SOA 1050, which amplifies the optical data signal, and directs the amplified optical data signal to the PIN photodetector 1030 for detection of the optical data signal and recovery of the data transmitted by the remote optical node. It should be appreciated that the optical transceiver 1001 may include other elements that may be involved in supporting communication of data by the optical transceiver 1001 of the optical communication device 1000.

[0068] During an optical detection measurement, the optical transceiver 1001 receives an optical test signal (e.g., a monitoring signal received over the optical fiber 1002 from a remote optical communication device or a back-reflected OTDR signal received over the optical fiber 1002). The duplexer 1040 directs the optical test signal, as well as the received optical data signal, to the PIN photodetector 1030. This results in mixing of the optical data signal and the optical test signal to form a mixed signal that is provided from the duplexer to the SOA 1050. The SOA 1050 amplifies the mixed signal to form an amplified mixed signal and provides the amplified mixed signal to the PIN photodetector 1030. A tap 1051, disposed between the SOA 1050 and the PIN photodetector 1030, taps a small amount of optical power from the amplified mixed signal to form a detection signal and directs the detection signal to additional components configured to support optical polarization and phase monitoring. It should be noted that the sensing channel may be modulated at any suitable data rate, and in at least some example embodiments, may be modulated at a rate significantly lower than that of the optical data channel to enable sensing solutions that support relatively low complexity and relatively low power consumption.

[0069] During optical detection measurements, the optical transceiver 1001 determines optical polarization and phase information based on EML technology. The detection signal from the tap 1051 is provided to the EAM 1070. The detection signal is mixed with a local oscillator signal provided by an injection-locked LO DFB laser 1080 associated with the EAM 1070 to provide a mixed signal associated with the EAM 1070. The mixed signal from the EAM 1070 is provided to a filter 1090, which filters the mixed signal and filters the low-frequency monitoring signal from the high-speed data signal to produce a filtered signal. The filtered signal is provided from the filter 1090 to a detection DSP 1099, which performs processing based on the filtered signal to determine optical polarization and phase information. Here, the filtered signal can be used as an analysis signal that can be analyzed or otherwise processed by the DSP 1099 to determine polarization and / or phase information. It should be appreciated that the operation of the optical transceiver 1001 for optical sensing is similar to that of the optical transceiver 901 of FIG. 9, except that only a single EML is used, thereby eliminating the need for a PBS and EML pair as used in the transceiver 901 of FIG. 9, thereby reducing complexity and cost.

[0070] FIG. 11 illustrates an example embodiment of an optical communication device including an optical transceiver configured to support optical power, polarization, and phase monitoring, where the optical polarization and phase monitoring is based on optical multiplexing of the sensed signal and subsequent processing of the mixed signal in the electrical domain.

[0071] Optical communication device 1100 includes optical transceiver 1101. Optical transceiver 1101 is configured to support optical data communication as well as optical detection measurements (e.g., to monitor power, polarization, and phase), and may be configured to support optical data communication and optical detection measurements simultaneously (e.g., using a dedicated wavelength for the optical detection measurements outside the range of wavelengths used for optical data communication) or separately (e.g., by switching between optical data communication and optical detection measurements based on time division multiplexing between the optical data communication and the optical detection measurements). Optical transceiver 1101 includes optical fiber 1102, DFB laser 1110, EAM 1120, PIN photodetector 1130, triplexer 1140, SOA 1150, and various additional components configured to support optical polarization and phase monitoring (e.g., polarizing beam splitter (PBS) 1160, a pair of EAMs 1170-1 and 1170-2 (collectively, EAMs 1170), and a pair of LO DFB lasers 1180-1 and 1180-2 (collectively, LO DFB lasers 1180). Here, unlike optical transceivers 900 and 1000 of FIGS. 9 and 10, respectively, sensing measurements are based on triplexer 1140 at a downstream data communication wavelength as λ1 and a third wavelength (λ) that is separated from the upstream data communication wavelength λ2. s Note that this is based on the use of a detection DSP 1199 configured to support processing of the mixed signal in the electrical domain to monitor polarization and phase. In this optical multiplexing case, the detection signal is already optically extracted by the triplexer 1040, so no additional electrical low-pass filtering is required. The optical communication device 1100 further includes a detection DSP 1199 configured to support processing of the mixed signal in the electrical domain to monitor polarization and phase.

[0072] The optical transceiver 1101 is configured to support transmission of optical data signals to and reception of optical data signals from a remote optical node during optical data communication. The optical transceiver 1101 is configured to transmit data to the remote optical node using a DFB laser 1110, an EAM 1120, and a triplexer 1140, e.g., the DFB laser 1110 provides an optical signal, the EAM 1120 modulates data onto the optical signal to form an optical data signal, and the triplexer 1140 directs the optical data signal onto the optical fiber 1102 for propagation to the remote optical node. Optical transceiver 1101 is configured to receive data from a remote optical node using triplexer 1140, SOA 1150, and PIN photodetector 1130, e.g., triplexer 1140 receives an optical data signal on optical fiber 1102, directs the optical data signal to SOA 1150, which amplifies the optical data signal, and directs the amplified optical data signal to PIN photodetector 1130 for detection of the optical data signal and recovery of data transmitted by the remote optical node. It should be understood that optical transceiver 1101 may include other elements that may be involved in supporting communication of data by optical transceiver 1101 of optical communication device 1100.

[0073] During the optical detection measurement, the optical transceiver 1101 determines optical polarization and phase information based on EML techniques. During the optical detection measurement, the optical transceiver 1101 receives an optical test signal (e.g., a monitoring signal received through the optical fiber 1102 from a remote optical communication device or a back-reflected OTDR signal received through the optical fiber 1102). As indicated above, the optical test signal is transmitted at a third wavelength (λ ) that is distinct from the wavelengths (λ 1 and λ 2 ) used for data communication. s) is used. The triplexer 1140 separates the optical test signal from the optical data signal and provides the optical test signal to the PBS 1160. The PBS 1160 separates the orthogonal polarization states to form separated optical signals and provides the separated optical signals to the EAMs 1170-1 and 1170-2, respectively (e.g., a first optical signal based on a first polarization is provided to the EAM 1170-1, and a second optical signal based on a second polarization is provided to the EAM 1170-2). The separated optical signals are mixed with local oscillator signals provided by injection-locked LO DFB lasers 1180-1 and 1180-2 associated with the EAMs 1170-1 and 1170-2, respectively, to provide mixed signals associated with the EAMs 1170-1 and 1170-2, respectively. The mixed signals from EAM 1170-1 and 1170-2 are provided to detection DSP 1199, which performs processing based on the mixed signals to determine optical polarization and phase information, where EAM 1170 operates as a sensor providing a detected signal, and the detected signal from EAM 1170 is provided to detection DSP 1199, which performs processing based on the detected signal to determine optical polarization and phase information, where the detected signal may be used as an analysis signal that may be analyzed or otherwise processed by DSP 1199 to determine polarization and / or phase information.

[0074] FIG. 12 illustrates an example embodiment of an optical communication device including an optical transceiver configured to support optical power, polarization, and phase monitoring, where the optical polarization and phase monitoring is based on optical multiplexing of the sensed signal and subsequent processing of the mixed signal in the electrical domain.

[0075] Optical communication device 1200 includes optical transceiver 1201. Optical transceiver 1201 is configured to support optical data communication and optical detection measurements (e.g., to monitor power, polarization, and phase), and may be configured to support optical data communication and optical detection measurements simultaneously (e.g., using a dedicated wavelength for the optical detection measurements outside the range of wavelengths used for optical data communication) or separately (e.g., by switching between the optical data communication and the optical detection measurements based on time division multiplexing between the optical data communication and the optical detection measurements). Optical transceiver 1201 includes optical fiber 1202, DFB laser 1210, EAM 1220, PIN photodetector 1230, triplexer 1240, SOA 1250, and various additional components (e.g., EAM 1270, LO DFB laser 1280) configured to support optical polarization and phase monitoring. Here, unlike the optical transceivers 900 and 1000 of FIGS. 9 and 10, respectively, the sensing measurement is based on a triplexer 1240 at a downstream data communication wavelength as λ1 and a third wavelength (λ) that is separated from the upstream data communication wavelength λ2. s Note that this is based on the use of a detection DSP 1299 configured to support processing of the mixed signal in the electrical domain to monitor polarization and phase. In this optical multiplexing case, the detection signal is already optically extracted by the triplexer 1240, so no additional electrical low-pass filtering is required. The optical communication device 1200 further includes a detection DSP 1299 configured to support processing of the mixed signal in the electrical domain to monitor polarization and phase.

[0076] Optical transceiver 1201 is configured to support transmission of optical data signals to and reception of optical data signals from a remote optical node during optical data communication. Optical transceiver 1201 is configured to transmit data to a remote optical node using DFB laser 1210, EAM 1220, and triplexer 1240, e.g., DFB laser 1210 provides an optical signal, EAM 1220 modulates data onto the optical signal to form an optical data signal, and triplexer 1240 directs the optical data signal onto optical fiber 1202 for propagation to the remote optical node. Optical transceiver 1201 is configured to receive data from a remote optical node using triplexer 1240, SOA 1250, and PIN photodetector 1230, e.g., triplexer 1240 receives an optical data signal on optical fiber 1202, directs the optical data signal to SOA 1250, which amplifies the optical data signal, and directs the amplified optical data signal to PIN photodetector 1230 for detection of the optical data signal and recovery of data transmitted by the remote optical node. It should be understood that optical transceiver 1201 may include other elements that may be involved in supporting communication of data by optical transceiver 1201 of optical communication device 1200.

[0077] During the optical detection measurement, the optical transceiver 1201 determines optical polarization and phase information based on EML techniques. During the optical detection measurement, the optical transceiver 1201 receives an optical test signal (e.g., a monitoring signal received through the optical fiber 1202 from a remote optical communication device or a back-reflected OTDR signal received through the optical fiber 1202). As indicated above, the optical test signal is transmitted at a third wavelength (λ ) that is distinct from the wavelengths (λ 1 and λ 2 ) used for data communication. s) is used. The triplexer 1240 separates the optical test signal from the optical data signal and provides the optical test signal to the EAM 1270. The test signal is mixed with a local oscillator signal provided by an injection-locked LO DFB laser 1280 associated with the EAM 1270 to provide a mixed signal associated with the EAM 1270. Here, the EAM 1270 operates as a sensor providing a detection signal, which is provided to the detection DSP 1299, which performs processing based on the detection signal to determine optical polarization and phase information. Here, the detection signal can be used as an analysis signal that can be analyzed or otherwise processed by the DSP 1299 to determine polarization and / or phase information. It should be appreciated that the operation of the optical transceiver 1201 for optical sensing is similar to that of the optical transceiver 1101 of FIG. 11, except that only a single EML is used, thereby eliminating the need for a PBS and EML pair as used in the transceiver 1101 of FIG. 11, thus reducing complexity and cost.

[0078] FIG. 13 illustrates an example embodiment of an optical communication device including an optical transceiver configured to support optical power, polarization, and phase monitoring, where the optical polarization and phase monitoring is based on optical multiplexing of the sensed signal and subsequent processing of the mixed signal in the electrical domain.

[0079] The optical communication device 1300 includes an optical transceiver 1301. The optical transceiver 1301 is configured to support optical data communication and optical detection measurements (e.g., to monitor power, polarization, and phase), and may be configured to support the optical data communication and optical detection measurements simultaneously (e.g., using a dedicated wavelength for the optical detection measurements outside the range of wavelengths used for the optical data communication) or separately (e.g., by switching between the optical data communication and the optical detection measurements based on time division multiplexing between the optical data communication and the optical detection measurements). The optical transceiver 1301 includes an optical fiber 1302, an SOA 1303, a DFB laser 1310, an EAM 1320, a PIN photodetector 1330, a triplexer 1340, and various additional components (e.g., an EAM 1370, a LO DFB laser 1380) configured to support optical polarization and phase monitoring. Here, unlike the optical transceivers 900 and 1000 of FIGS. 9 and 10, respectively, the sensing measurement is based on a triplexer 1340 at a downstream data communication wavelength as λ1 and a third wavelength (λ) that is separated from the upstream data communication wavelength λ2. s Note that this is based on the use of a detection DSP 1399 configured to support processing of the mixed signal in the electrical domain to monitor polarization and phase. In this optical multiplexing case, the detection signal is already optically extracted by the triplexer 1340, so no additional electrical low-pass filtering is required. The optical communication device 1300 further includes a detection DSP 1399 configured to support processing of the mixed signal in the electrical domain to monitor polarization and phase.

[0080] Optical transceiver 1301 is configured to support the transmission of optical data signals to and reception of optical data signals from remote optical nodes during optical data communications. Optical transceiver 1301 is configured to transmit data to remote optical nodes using DFB laser 1310, EAM 1320, and triplexer 1340, e.g., DFB laser 1310 provides an optical signal, EAM 1320 modulates data onto the optical signal to form an optical data signal, and triplexer 1340 directs the optical data signal onto optical fiber 1302 for propagation to the remote optical node. Optical transceiver 1301 is configured to receive data from remote optical nodes using triplexer 1340 and PIN photodetector 1330, e.g., triplexer 1340 receives an optical data signal on optical fiber 1302 and directs the optical data signal to PIN photodetector 1330 for detection of the optical data signal and recovery of data transmitted by the remote optical node. In either case, the SOA 1303 supports amplification of the optical data signal (e.g., as a pre-amplifier for received optical data signals and a post-amplifier for transmitted optical data signals). It should be understood that the optical transceiver 1301 may include other elements that may be involved in supporting communication of data by the optical transceiver 1301 of the optical communication device 1300.

[0081] During the optical detection measurement, the optical transceiver 1301 determines optical polarization and phase information based on EML techniques. During the optical detection measurement, the optical transceiver 1301 receives an optical test signal (e.g., a monitoring signal received through the optical fiber 1302 from a remote optical communication device or a back-reflected OTDR signal received through the optical fiber 1302). As indicated above, the optical test signal is transmitted at a third wavelength (λ ) that is distinct from the wavelengths (λ ) used for data communication. s) is used. The triplexer 1340 separates the optical test signal from the optical data signal and provides the optical test signal to the EAM 1370. The test signal is mixed with a local oscillator signal provided by an injection-locked LO DFB laser 1380 associated with the EAM 1370 to provide a mixed signal associated with the EAM 1370. The mixed signal from the EAM 1370 is provided to the detection DSP 1399, which performs processing based on the mixed signal to determine optical polarization and phase information. Here, the mixed signal can be used as an analysis signal that can be analyzed or otherwise processed by the DSP 1399 to determine polarization and / or phase information. It should be appreciated that the operation of the optical transceiver 1301 for optical sensing is similar to that of the optical transceiver 1201 of FIG. 12, except that the SOA 1303 disposed between the optical fiber 1302 and the triplexer 1340 provides amplification of the optical test signal received by the optical transceiver 1301 and is used to determine optical polarization and phase information.

[0082] FIG. 14 illustrates an exemplary embodiment of a method for use by an optical communication device to support optical monitoring. While presented primarily as being performed sequentially, it should be understood that at least some of the functions of method 1400 may occur simultaneously or in a different order than presented with respect to FIG. 14 . Method 1400 begins at block 1401. At block 1410, an optical test signal is separated from a set of optical signals including an optical data communication signal and an optical test signal. At block 1420, the optical test signal is converted to an analytical signal based on electroabsorption-modulated laser performance. At block 1430, at least one of polarization information of the optical test signal or phase information of the optical test signal is determined based on digital signal processing based on the analytical signal. At block 1499, method 1400 ends.

[0083] It should be appreciated that various exemplary embodiments of optical communications devices configured to support polarization and phase monitoring in addition to power monitoring (e.g., exemplary embodiments for supporting polarization and phase monitoring in addition to power monitoring in optical communications devices such as those presented with respect to Figures 9-14) may be provided in various other manners.

[0084] FIG. 15 illustrates an exemplary embodiment of a computer suitable for use in performing the various functions presented herein.

[0085] Computer 1500 includes a processor 1502 and a memory 1504. Processor 1502 may be a processing unit (e.g., a central processing unit (CPU), a graphics processing unit (GPU), etc.), a portion of a processing unit (e.g., a set of processor cores, a single processor core, etc.), etc. Memory 1504 may be random access memory (RAM), read-only memory (ROM), etc. In at least some example embodiments, computer 1500 includes at least one processor and at least one memory that stores instructions that, when executed by the at least one processor, cause computer 1500 to perform various functions presented herein.

[0086] Computer 1500 may also include cooperating elements 1505. Cooperating elements 1505 may include hardware, firmware, software, etc., as well as various combinations thereof. Cooperating elements 1505 may be processes that can be loaded into memory 1504 and executed by processor 1502 to implement various functions presented herein (in which case, for example, cooperating elements 1505 (including associated data structures) may be stored on a non-transitory computer-readable storage medium such as a storage device or other suitable type of storage element (e.g., magnetic drive, optical drive, solid-state drive, etc.)).

[0087] The computer 1500 may also include one or more input / output devices 1506. The input / output devices 1506 include one or more of user input devices (e.g., a keyboard, keypad, mouse, microphone, camera, etc.), user output devices (e.g., a display, speakers, etc.), one or more network communication devices or elements (e.g., input ports, output ports, receivers, transmitters, transceivers, etc.), one or more storage devices (e.g., a tape drive, floppy drive, hard disk drive, solid state drive, etc.), etc., as well as various combinations thereof.

[0088] It should be understood that computer 1500 may represent a general architecture and functionality suitable for implementing the functional elements described herein, portions of the functional elements described herein, and the like, as well as various combinations thereof. For example, computer 1500 may provide a general architecture and functionality suitable for implementing one or more elements presented herein. For example, computer 1500 may provide a general architecture and functionality suitable for implementing at least one of an OLT or portion thereof, an ONU or portion thereof, an optical transceiver or portion thereof, an optical receiver or portion thereof, an optical communication device or portion thereof, and the like, as well as various combinations thereof.

[0089] It will be understood that at least some of the functionality presented herein may be implemented in software (e.g., via implementation of the software on one or more processors for execution on a general-purpose computer (e.g., via execution by one or more processors) to provide a special-purpose computer, etc.) and / or may be implemented in hardware (e.g., using a general-purpose computer, one or more application-specific integrated circuits, and / or any other hardware equivalents).

[0090] It should be understood that at least a portion of the functionality presented herein may be implemented in hardware, for example, as circuitry that cooperates with a processor to perform various functions. Some of the functions / elements described herein may also be implemented as a computer program product, where computer instructions, when processed by a computer, adapt the operation of the computer such that the methods and / or techniques described herein are invoked or otherwise provided. Instructions for invoking the various methods may be stored on fixed or removable media (e.g., non-transitory computer-readable media), transmitted via a data stream of a broadcast or other signal-bearing medium, and / or stored in memory within a computing device that operates according to the instructions.

[0091] It should be understood that the term "non-transitory" as used herein is a qualification of the medium itself (i.e., being tangible, not a signal) as opposed to a qualification of the permanence of the data storage (e.g., RAM vs. ROM).

[0092] As used herein, "at least one of " and "at least one of: " and similar phrases, when a list of two or more elements is joined by "and" or "or", mean at least one of the elements, or at least two or more of the elements, or at least all of the elements.

[0093] As used herein, the term "or" should be understood to refer to a non-exclusive "or" unless otherwise indicated (e.g., use of "or" or "or alternatively").

[0094] While various embodiments incorporating the teachings presented herein have been shown and described in detail herein, it should be understood that those skilled in the art can readily devise many other polarized embodiments that also incorporate these teachings. [Explanation of symbols]

[0095] 100 Passive Optical Networks 111, 121-1, 121-N, 200, 300, 400, 600, 700, 900, 1000, 1100, 1200, 1300 Optical communication devices 112, 122-1, 122-N, Optical Monitoring and Detection Devices 130 Optical Distribution Network 201 Optical Signal 210 Divider 212 first optical signal portion 213 Second optical signal part 220 Polarization-independent photodetector 230 Polarization-Sensitive Photodetector 231 Modulator-Detector 232 Modulation Function 233 Detection Function 301, 401, 601, 701, 901, 1001, 1101, 1201, 1301 Optical Transceivers 302, 402, 602, 702, 902, 1002, 1102, 1202, 1302 optical fiber 310, 410, 610, 710, 910, 1010, 1110, 1210, 1310 Distributed Feedback Lasers 320, 420, 620, 720, 920, 1020, 1120, 1220, 1320 Electroabsorption Modulator 330, 430, 630, 730, 760, 930, 1030, 1130, 1230, 1330 PIN photodetector 340, 440, 640, 740, 940, 1040 duplexer 403 Semiconductor Optical Amplifier 500 EAM electronic circuit 510 Bias Tee 520 Driver 530 Biasing Source and OTDR Receiver 605, 705 splitter 800 ways 801, 810, 820, 830, 899 blocks 951, 1051 taps 960, 1160 Polarizing Beam Splitter 980-1, 980-2, 1080, 1180-1, 1180-2, 1280, 1380 LO DFB laser 990-1, 990-2, 1090 filters 999, 1099, 1199, 1299, 1399 Detection DSP 1140, 1240, 1340 triplexer 1400 methods Blocks 1401, 1410, 1420, 1430, and 1499 1502 processor 1504 memory 1505 Collaborative Elements 1506 Input / Output Devices

Claims

1. a divider configured to divide the optical signal into a first optical signal portion and a second optical signal portion; a polarization independent photodetector configured to monitor a power level of the optical signal based on the first optical signal portion; a polarization-sensitive photodetector configured to monitor the polarization of the optical signal based on the second optical signal portion; An optical communication device comprising: An apparatus comprising:

2. 10. The apparatus of claim 1, wherein the polarization-sensitive photodetector comprises a modulator-detector configured to support modulation and detection functions.

3. 3. The apparatus of claim 1 or 2, wherein the polarization-sensitive photodetector comprises a reverse-biased electro-absorption modulator based on the quantum-confined Stark effect (QCSE).

4. 4. The device of claim 1, wherein the polarization-sensitive photodetector comprises a polarization-sensitive interferometric modulator and a detector, wherein a first side of the polarization-sensitive interferometric modulator is connected to the divider and a second side of the polarization-sensitive interferometric modulator is connected to the detector.

5. The device of claim 4, wherein the polarization-sensitive interferometric modulator comprises a Mach-Zehnder modulator or a ring modulator.

6. 6. The apparatus of claim 1, wherein the optical communication device is configured to detect a change in polarization of the optical signal based on determining that the power level of the first optical signal portion remains relatively constant at the polarization-independent photodetector, while the absorption level of the second optical signal portion changes at the polarization-sensitive photodetector.

7. Optical communication devices determining that the power level of the first optical signal portion changes at the polarization-independent photodetector; or Determining that the power level of the first optical signal portion remains relatively constant at the polarization-independent photodetector while the absorption level of the second optical signal portion changes at the polarization-sensitive photodetector.

7. The apparatus of claim 1, configured to detect a condition or event associated with an optical fiber based on one of:

8. 8. The apparatus of claim 1, wherein the optical signal comprises a back-reflected optical time domain reflectometry signal received at an optical communication device.

9. 8. Apparatus according to any one of claims 1 to 7, wherein the optical signal comprises a monitoring optical signal received at the optical communication device from a remote optical communication device via an optical fiber.

10. 8. The apparatus of claim 1, wherein the optical signal comprises a broadband detection signal comprising a first wavelength and a second wavelength, the first optical signal portion being at the first wavelength and the second optical signal portion being at the second wavelength.

11. 8. The apparatus of claim 1, wherein the optical signal includes a wavelength outside a data transmission wavelength range used for data transmission by the optical communication device, and the optical communication device is configured to support parallel operations of data transmission by the optical communication device and monitoring by the optical communication device based on the optical signal.

12. 8. The apparatus of claim 1, wherein the optical signal includes a wavelength within a data transmission wavelength range used by the optical communication device for data transmission, and the optical communication device is configured to switch between data transmission by the optical communication device and monitoring by the optical communication device based on the optical signal.

13. The divider comprises a wavelength splitter, and the optical communications device is configured to operate as both a data communications transceiver for optical data signals and an optical time domain reflectometry transceiver for optical time domain reflectometry signals, and the optical communications device comprises: a semiconductor optical amplifier disposed between the wavelength splitter and the optical fiber, the semiconductor optical amplifier configured to amplify the optical data signal and the optical time domain reflectometry signal; a laser connected to the polarization-sensitive photodetector, the laser configured to generate light that is modulated at the polarization-sensitive photodetector for an optical data signal; Furthermore, 13. The apparatus of claim 1, wherein the wavelength splitter is configured to connect a first wavelength between the wavelength splitter and the polarization-independent photodetector and to connect a second wavelength, different from the first wavelength, between the wavelength splitter and the polarization-sensitive photodetector.

14. Optical communication devices Supporting the initiation of an optical time domain reflectometry test by switching off the laser, ceasing modulation of the communications data by the polarization-sensitive photodetector, and modulating the semiconductor amplifier to generate an optical time domain reflectometry pulse; and Supporting optical time domain reflectometry measurements by receiving a back-reflected optical time domain reflectometry signal, detecting a reflected power of the back-reflected optical time domain reflectometry signal with a polarization-independent photodetector, and obtaining information regarding variations in polarization of the back-reflected optical time domain reflectometry signal based on detection of at least one polarization with the polarization-sensitive photodetector.

14. The apparatus of claim 13, configured to perform optical time domain reflectometry testing by:

15. Optical communication devices a driver configured to provide an electrical drive signal for the optical data signal; an optical time domain reflectometry electrical receiver configured to receive an electrical sensing signal associated with the second optical signal portion; an electrical circuit configured to separate the electrical drive signal for the optical data signal and the electrical sense signal associated with the second optical signal portion using at least one of time multiplexing or frequency multiplexing; 15. The apparatus of claim 1, further comprising:

16. 16. The apparatus of claim 15, wherein the electrical circuit comprises an amplification path configured to connect a driver to the polarization-sensitive photodetector and a detection path configured to connect the polarization-sensitive photodetector to the optical time domain reflectometry electrical receiver, and the driver includes a time switch configured to switch the electrical circuit between using the amplification path and using the detection path.

17. Optical communication devices sequentially modulating communication data by the polarization-sensitive photodetector based on sequentially emitting optical power by a laser associated with the polarization-sensitive photodetector to form an optical data signal; continuous detection of the received optical data signal by a polarization-independent photodetector; modulating the first optical amplifier to generate an optical time domain reflectometry signal; continuously driving a second optical amplifier with a DC driver to amplify the optical data signal and the optical time domain reflectometry signal; detecting the received optical data signal and the back-reflected optical time domain reflectometry signal with a polarization-independent photodetector; detection of the back-reflected optical time domain reflectometry signal by an optical time domain reflectometry electrical receiver based on absorption of the back-reflected optical time domain reflectometry signal by a polarization-sensitive photodetector via a low frequency path in an electrical circuit; 16. The device of claim 15, configured to support continuous use of optical data communication and optical sensing based on

18. Optical communication devices an optical amplifier pair including a first optical amplifier configured to generate an optical time domain reflectometry signal that is modulated and transmitted by the optical communication device, and a second optical amplifier configured to support sequential amplification of both an optical data signal transmitted by the optical communication device and the optical time domain reflectometry signal transmitted by the optical communication device; an optical time domain reflectometry driver configured to generate an optical time domain reflectometry drive signal for the first optical amplifier; a DC driver configured to generate a DC drive signal for the second optical amplifier; 18. The apparatus of claim 1, comprising:

19. 19. The apparatus of any one of claims 1 to 18, wherein the optical communication device comprises at least one of an optical receiver or an optical transceiver.

20. a divider configured to separate the optical test signal from a set of optical signals including the optical data communication signal and the optical test signal; a circuit configured to convert the optical test signal into an analytical signal based on electroabsorption modulated laser capabilities; a digital signal processor configured to determine at least one of polarization information of the optical test signal or phase information of the optical test signal based on the analysis signal; An apparatus comprising:

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