Patent Description:
Most optical communication networks are employed with optical supervisory channels (OSCs) and optical time domain reflectometer (OTDRs). The International Telecommunication Union ITU-T G. <NUM> recommendation defines an OSC as "A channel that is accessed at each optical line amplifier site that is used for maintenance purposes including (but not limited to) remote site alarm reporting, communication necessary for fault location, and orderwire. The Optical Supervisory Channel is not used to carry payload traffic".

In a practical implementation, the OSC is implemented on a wavelength λOSC that is usually outside the transmission band, such as for example, C-band. Typical wavelengths associated with the OSC are <NUM>, <NUM>, <NUM> or another proprietary wavelength. The OSC carries information about dense wavelength division multiplexed (DWDM) optical signals as well as remote conditions at the optical terminal or amplifier site. The OSC is also normally used for remote software upgrades, network management information and clock synchronization. The OSC signal structure is vendor specific, even if the ITU standard suggests using an OC-<NUM> signal structure. Further, the OSC is always terminated at intermediate nodes, where it receives local information before retransmission. However, wavelengths associated traffic signals are terminated at endpoints of a light path.

Whereas, OTDRs are widely used in the area of testing fiber characteristics. The OTDRs measure the loss of optical signal strength in a section and the total loss encountered in an end-to-end network by tracking the attenuation in the optical signal. The OTDR operates by launching a short pulse of light of a predetermined wavelength λOTDR, into the fiber, and measuring the reflected signal as a function of time. Usually λOTDR is also outside the transmission band.

In many applications, such as, for example, <NUM> or <NUM>, there is a requirement of clock synchronization. Most of the applications rely on optical communication networks to deliver synchronized clock over distance and often times the OSC is used to synchronize the clock. The clock synchronization is performed by OSC/OTDR module operating under OSC mode. During OTDR mode, there is an increase in clock synchronization error. Prior to <NUM> technology, the intermittent OSC was satisfying the clock synchronization requirements to a great extent.

However, <NUM> and similar applications have a much higher clock synchronization requirement. This challenge of higher clock synchronization requirement may be exacerbated by certain proposed enhancements to existing wireless communication systems as well as next-generation wireless communication designs. Such enhancements and designs include OSC/OTDR module can function as OSC or OTDR in an interleaving manner. Document <CIT> describes data center interconnections, which encompass WSCs as well as traditional data centers. According to this document the date center interconnections have become both a bottleneck and a cost/power issue for cloud computing providers, cloud service providers and the users of the cloud generally. Fiber optic technologies already play critical roles in data center operations and will increasingly in the future. The goal is to move data as fast as possible with the lowest latency with the lowest cost and the smallest space consumption on the server blade and throughout the network. Accordingly, it would be beneficial for new fiber optic interconnection architectures to address the traditional hierarchal time-division multiplexed (TDM) routing and interconnection and provide reduced latency, increased flexibility, lower cost, lower power consumption, and provide interconnections exploiting NxMxD Gbps photonic interconnects wherein N channels are provided each carrying M wavelength division signals at D Gbps.

Document <CIT> discloses an optical fiber communication line monitoring method and device and a computer storage medium, wherein the method comprises the steps of: determining the level of a current time slice which comprises a first level of a period of time and a second level of another period of time; and according to the level of the current time slice, triggering an OTDR monitoring unit corresponding to the level to start measurement work or an OSC monitoring unit to start channel monitoring work.

Document <CIT> describes optical service channel (OSC) systems and methods over high loss links utilizing redundant telemetry channels. A first telemetry channel provides a low bandwidth communication channel used when Raman amplification is unavailable on a high loss link for supporting a subset of operations, administration, maintenance, and provisioning (OAM And P) communication. A second telemetry channel provides a high bandwidth communication channel for when Raman amplification is available to support full OAM And P communication. The first and second telemetry operate cooperatively ensuring nodal OAM And P communication over high loss links (e.g., <NUM> dB) regardless of operational status of Raman amplification.

The present invention is set out by the set of appended claims. An object of the present disclosure is to provide an optical transceiver. The disclosure presented herein employs a first optical time domain reflectometer (OTDR) module configured to generate a first OTDR signal, and a second OTDR signal, the second OTDR signal being a delayed version of the first OTDR signal, a first optical supervisory channel (OSC) transmitter configured to generate a first OSC signal, and a second OSC signal, the second OSC signal being a delayed version of the first OSC signal, a first wavelength division multiplexer (WDM) configured to transmit the first OSC signal interleaved with the first OTDR signal on a first optical fiber and a second WDM configured to transmit the second OSC signal interleaved with the second OTDR signal on a second optical fiber, wherein at any time during operation of the optical transceiver, at least one of the first and second OSC signals is present on a corresponding one of the first and second optical fibers.

In accordance with other aspects of the present disclosure the optical transceiver, further comprising an OSC receiver operatively connected to the first and second WDMs, the OSC receiver being configured to receive a third OSC signal interleaved with a third OTDR signal from the first WDM, receive a fourth OSC signal interleaved with a fourth OTDR signal from the second WDM and combine the third and fourth OSC signals to form an uninterrupted signal containing clock synchronization information.

In accordance with other aspects of the present disclosure the optical transceiver, wherein the OSC receiver further comprises a first delay element configured to provide delay adjustments to the third OSC signal interleaved with the third OTDR signal and a second delay element configured to provide delay adjustments to the fourth OSC signal interleaved with the fourth OTDR signal from the second WDM.

In accordance with other aspects of the present disclosure the optical transceiver, further comprising a controller configured to provide control signals to the first delay element and the second delay element.

In accordance with other aspects of the present disclosure the optical transceiver, further comprising a radio frequency (RF) switch configured to switch between the third OSC signal interleaved with the third OTDR signal and the fourth OSC signal interleaved with the fourth OTDR signal to form the uninterrupted signal containing clock synchronization information.

In accordance with other aspects of the present disclosure the optical transceiver, further comprising further comprising a logic processor configured to provide control signals to the RF switch, the controller and a peer optical transceiver.

In accordance with other aspects of the present disclosure the optical transceiver, wherein the first, second, third and fourth OSC signals include a switch window to assist the smooth switching operation without loss of any relevant information.

In accordance with other aspects of the present disclosure the optical transceiver, wherein the third OSC signal interleaved with the third OTDR signal and the fourth OSC signal interleaved with the fourth OTDR signal are received from a peer optical transceiver.

In accordance with other aspects of the present disclosure, there is provided a method implemented in an optical transceiver. The disclosure presented herein performs, generating a first optical time domain reflectometer (OTDR) signal and a second OTDR signal, the second OTDR signal being a delayed version of the first OTDR signal, generating a first optical supervisory channel (OSC) signal and a second OSC signal, the second OSC signal being a delayed version of the first OSC signal, interleaving the first OSC signal and the first OTDR signal, interleaving the second OSC signal and the second OTDR signal, transmitting the first OSC signal interleaved with the first OTDR signal on a first optical fiber, and transmitting the second OSC signal interleaved with the second OTDR signal on a second optical fiber, wherein at any time during operation of the optical transceiver, at least one of the first and second OSC signals is present on a corresponding one of the first and second optical fibers.

In accordance with other aspects of the present disclosure, the method implemented in an optical transceiver, further comprising receiving a third OSC signal interleaved with a third OTDR signal, receiving a fourth OSC signal interleaved with a fourth OTDR signal, and combining the third and fourth OSC signals to form an uninterrupted signal containing clock synchronization information.

In accordance with other aspects of the present disclosure, the method implemented in an optical transceiver, further comprising providing delay adjustments to the third OSC signal interleaved with the third OTDR signal and the fourth OSC signal interleaved with the fourth OTDR signal from the second WDM.

In accordance with other aspects of the present disclosure, the method implemented in an optical transceiver, wherein providing delay adjustments to the third OSC signal interleaved with the third OTDR signal and the fourth OSC signal interleaved with the fourth OTDR signal are in accordance control signals as supplied by a logic processing unit.

In accordance with other aspects of the present disclosure, the method implemented in an optical transceiver, wherein the delay adjustments are provided by a controller.

In accordance with other aspects of the present disclosure, the method implemented in an optical transceiver, further comprising, receiving the third OSC signal interleaved with the third OTDR signal and the fourth OSC signal interleaved with the fourth OTDR signal from a peer optical transceiver.

In accordance with other aspects of the present disclosure, the method implemented in an optical transceiver, further comprising switching between the third OSC signal interleaved with the third OTDR signal and the fourth OSC signal interleaved with the fourth OTDR signal to form the uninterrupted signal containing clock synchronization information.

In accordance with other aspects of the present disclosure, the method implemented in an optical transceiver, wherein the first, second, third and fourth OSC signals includes a switch window to assist the smooth switching operation without loss of any relevant information.

In accordance with other aspects of the present disclosure, the method implemented in an optical transceiver, wherein forming the uninterrupted signal containing clock synchronization information further comprises scanning the first OSC signal interleaved with the first OTDR signal and the second OSC signal interleaved with the second OTDR signal for delay pre-compensations until a correlation peak is found.

In accordance with other aspects of the present disclosure, the method implemented in an optical transceiver, wherein forming the uninterrupted signal containing clock synchronization information comprises alternative switching between the first OSC signal interleaved with the first OTDR signal and the second OSC signal interleaved with the second OTDR signal in accordance with control signals as supplied by a logic processing unit.

In accordance with other aspects of the present disclosure, the method implemented in an optical transceiver, further comprises providing control signals to a peer optical transceiver by a logic processing unit in order to assist the peer optical transceiver in phase pre-adjustments.

The features and advantages of the present disclosure will become apparent from the following detailed description, taken in combination with the appended drawings, in which:.

It is to be understood that throughout the appended drawings and corresponding descriptions, like features are identified by like reference characters. Furthermore, it is also to be understood that the drawings and ensuing descriptions are intended for illustrative purposes.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the described embodiments appertain to.

<FIG>(Prior Art) depicts a high-level functional block diagram of a conventional optical communication network <NUM> directed to transmit and receive optical signals. The conventional optical communication network <NUM> includes optical transceivers 102a and 102b, and optical fibers 112a and 112b. It will be understood that other elements may be present, but are not illustrated for the purpose of tractability and simplicity.

As shown in <FIG>, the optical transceiver 102a includes OSC transmitter/OTDR-OSC receiver modules 104a and 104b, wavelength division multiplexers (WDMs) 110a and 110c, amplifiers 114a and 116a. Similarly, the optical transceiver 102b includes OSC transmitter/OTDR-OSC receiver modules 104c and 104d, wavelength division multiplexers (WDMs) 110b and 110d, amplifiers 114b and 116b.

The conventional optical communication network <NUM> is configured to multiplex and transmits main signals consisting of around <NUM> channels in C-band (typically <NUM>-<NUM>) with signals associated with OSC and OTDR outside C-band. OSC transmitter/OTDR-OSC receiver modules 104a and 104b employing OSC transmitter/OTDRs 106a and 106b are configured to generate signals at wavelengths λ<NUM>, and λ<NUM> respectively. The generated signals are associated with OSC and OTDR, interleaved, and transmitted towards the optical transceiver 102b. OSC transmitter/OTDRs 106c and 106d employing OSC receivers 108c and 108d are configured to receive λ<NUM> and λ<NUM> respectively.

In a similar manner, OSC transmitter/OTDR-OSC receiver modules 104c and 104d employing OSC transmitter/OTDRs 106c and 106d are configured to generate signals at wavelengths λ<NUM>, and λ<NUM> respectively. The generated signals are associated with OSC and OTDR, interleaved and transmitted towards optical transceiver 102a. It is to be understood that wavelengths λ<NUM> and λ<NUM> are different and transmitted over optical fiber 112a and wavelengths λ<NUM> and λ<NUM> are different and transmitted over optical fiber 112b. OSC transmitter/OTDRs 106a and 106b employing OSC receivers 108a and 108b are configured to receive λ<NUM>, and λ<NUM> respectively.

Further, the OSC transmitter/OTDR-OSC receiver modules 104a, 104b, 104c, and 104d provide clock synchronization information while transmitting signals associated with OSC. However, OSC transmitter/OTDR-OSC receiver modules 104a, 104b, 104c, and 104d fail to provide clock synchronization information while transmitting signals associated with OTDR. Resulting in clock synchronization error and putting a limit on high speed operations of the conventional optical communication network <NUM>.

To this end, <FIG> illustrates a high-level functional block diagram of an uninterrupted clock synchronization-based optical communication network <NUM> containing two optical transceivers 202a and 202b, in accordance with various embodiments discussed in the present disclosure. The uninterrupted clock synchronization-based optical communication network <NUM> includes optical transceivers 202a and 202b, and optical fibers 216a and 216b. It will be understood that other elements may be present, but are not illustrated for the purpose of tractability and simplicity.

As shown in <FIG>, the optical transceiver 202a includes an OSC transmitter/OTDR module 204a, an OSC receiver module 208a, wavelength division multiplexers (WDMs) 210a and 210b, amplifiers 212a and 214a. Similarly, the optical transceiver 202b includes an OSC transmitter/OTDR module 204b, an OSC receiver module 208b, wavelength division multiplexers (WDMs) 210c and 210d, amplifiers 212b and 214b.

The OSC transmitter/OTDR module 204a further employs a first OSC transmitter/OTDR 206a and a second OSC transmitter/OTDR 206b. The first OSC transmitter/OTDR 206a is configured to generate signals associated with OSC and OTDR at wavelengths λ<NUM> in an interleaved manner. Likewise, the second OSC transmitter/OTDR 206b may be configured to generate signals associated with OSC and OTDR at wavelengths λ<NUM> in an interleaved manner. Such that, for a window <NUM>, the information is associated OSC and for a window <NUM> the information is associated OTDR. In certain embodiments, signals associated with OSC and OTDR may be generated separately and then interleaved.

In certain embodiments, the first OSC transmitter/OTDR 206a and second OSC transmitter/OTDR 206b are configured to operate in synchronization and transmit clock synchronization information over OSC. In so doing, clock synchronization information may be split into two identical streams and transmitted by the first OSC transmitter/OTDR 206a and the second OSC transmitter/OTDR 206b.

<FIG> illustrates representative frames of information transmitted by the optical transceiver 202a toward the second optical transceiver 202b, in accordance with various embodiments discussed in the present disclosure. As shown, uninterrupted clock synchronization information 402a is split into two identical streams and is transmitted over the OSC using the first OSC transmitter/OTDR 206a and the second OSC transmitter/OTDR 206b. Each OSC window <NUM>, carrying clock synchronization information is interrupted by an OTDR window <NUM>. For example, the OSC transmitter/OTDR 206b transmitting clock synchronization information is first interrupted, the OSC transmitter/OTDR 206a transmitting clock synchronization information is then interrupted, and so on.

However, the OTDR windows <NUM> are designed such that at any given time, at least the first OSC transmitter/OTDR 206a or the second OSC transmitter/OTDR 206b is transmitting uninterrupted clock synchronization information. To this end, either of the OSC transmitter/OTDR 206a or the second OSC transmitter/OTDR 206b provides a time shift in clock synchronization information interleaved with OTDR information. Typically uninterrupted OSC windows <NUM> are significantly longer than the OTDR windows <NUM>, and hence there remains a significant overlap time between OSC windows <NUM> as provided by the OSC transmitter/OTDRs 206a and 206b.

Returning to <FIG>, main signals consisting of around <NUM> channels in C-band are pre-amplified using the amplifier 212a and are multiplexed using the WDM 212a with clock synchronization information interleaved with OTDR information as provided by the OSC transmitter/OTDR 206a. Further, this multiplexed information is transmitted towards the optical transceivers 202b using optical fiber 216a. Also, clock synchronization information interleaved with OTDR information as provided by the OSC transmitter/OTDR 206b is transmitted towards the optical transceivers 202b using the optical fiber 216b.

As shown in <FIG>, at the other end of the optical fibers 216a and 216b, optical transceivers 202b employing the OSC transmitter/OTDR module 204b further employs a third OSC transmitter/OTDR 206c and a fourth OSC transmitter/OTDR 206d. Third OSC transmitter/OTDR 206c is configured to generate signals associated with OSC and OTDR at wavelengths λ<NUM> in an interleaved manner. Likewise, fourth OSC transmitter/OTDR 206d is configured to generate signals associated with OSC and OTDR at wavelengths λ<NUM> in an interleaved manner. Such that, for a window <NUM>, the information is associated OSC and for a window <NUM> the information is associated OTDR.

It will be appreciated that, to efficiently utilize the wavelength resources, spatial area and optimize the overall cost of optical communication networks, in certain optical communication networks, OSCs and OTDR can be combined into one module OSC/OTDR and operated at same wavelength. Thus, OSC/OTDR module can function as OSC or OTDR in an interleaving manner. However, in an embodiment, the OSC transmitter/OTDR module 204a, the first OSC transmitter/OTDR 206a and the second OSC transmitter/OTDR 206b can be implemented as separate components. Also, each of the OSC transmitters can be implemented as a separate component from the respective OTDR modules.

Further, the third OSC transmitter/OTDR 206c and the fourth OSC transmitter/OTDR 206d are configured to operate in synchronization and transmit clock synchronization information over OSC. In so doing, clock synchronization information may be split into two identical streams and transmitted by the third OSC transmitter/OTDR 206a and the fourth OSC transmitter/OTDR 206b.

It will be appreciated that the optical transceiver 202b may operate in a similar manner as optical transceiver 202a. That is, optical transceiver 202b may be configured to pre-amplify main signals consisting of around <NUM> channels in C-band using the amplifier 212b and multiplex the amplified main signals with clock synchronization information interleaved with OTDR information as provided by the OSC transmitter/OTDR 206c using the WDM 210c. Further, this multiplexed information is transmitted towards the optical transceivers 202a using the optical fiber 216a. Also, clock synchronization information interleaved with OTDR information as provided by the OSC transmitter/OTDR 206d is transmitted towards the optical transceivers 202a using the optical fiber 216b.

It is to be understood that wavelengths λ<NUM> and λ<NUM> transmitted over the optical fiber 216a are different and wavelengths λ<NUM> and λ<NUM> transmitted over the optical fiber 216b are different. However, in certain embodiments, wavelength λ<NUM> may be approximately equal to wavelengths λ<NUM> or λ<NUM>. Similarly, wavelength λ<NUM> may be approximately equal to wavelengths λ<NUM> or λ<NUM>.

Further, the WDM 210a is configured to de-multiplex clock synchronization information interleaved with OTDR information at wavelength λ<NUM>, as received from the optical transceivers 202b and provides the de-multiplexed clock synchronization information interleaved with OTDR information to the OSC receiver module 208a. Similarly, the WDM 210b may be configured to de-multiplex main signals and clock synchronization information interleaved with OTDR information at wavelength λ<NUM>, as received from optical transceivers 202b and may provide the de-multiplexed main signals to the amplifier 214a and clock synchronization information interleaved with OTDR information to the OSC receiver module 208a.

In a similar manner, the WDM 210c may be configured to de-multiplex clock synchronization information interleaved with OTDR information at wavelength λ<NUM>, as received from the optical transceivers 202a and may provide the de-multiplexed clock synchronization information interleaved with OTDR information to the OSC receiver module 208b. Similarly, the WDM 210d may be configured to de-multiplex main signals and clock synchronization information interleaved with OTDR information at wavelength λ<NUM>, as received from the optical transceivers 202a and may provide the de-multiplexed main signals to the amplifier 214b and clock synchronization information interleaved with OTDR information to the OSC receiver module 208b.

<FIG> illustrates a basic block diagram of OSC receiver module 208a in the optical transceiver 202a, in accordance with various embodiments discussed in the present disclosure. As shown, the OSC receiver module 208a includes photo detectors 302a and 302b, delay elements 304a and 304b and a radio frequency (RF) switch <NUM>. It will be understood that other elements may be present, but are not illustrated for the purpose of tractability and simplicity.

As shown, photo detectors 302a and 302b may be configured to receive clock synchronization information interleaved with OTDR information at wavelengths λ<NUM> and λ<NUM> respectively. Further, photo detectors 302a and 302b may be configured to generate electrical signals corresponding to clock synchronization information interleaved with OTDR information at wavelengths λ<NUM> and λ<NUM> and supply the electrical signals to delay elements 304a and 304b for further processing.

Delay elements 304a and 304b may be configured to provide delay adjustments to the received electrical signals such that clock synchronization information interleaved with OTDR information at wavelengths λ<NUM> and λ<NUM> may be aligned and combined using the radio frequency (RF) switch <NUM> to form one uninterrupted signal corresponding to clock synchronization information.

<FIG> illustrates representative windows of information received by the OSC receiver module 208a, in accordance with various embodiments discussed in the present disclosure. As shown, the clock synchronization information alternates on each channel in such a manner that at any instant at least one channel is carrying clock synchronization information. Further, the duration of OSC window <NUM> is more than the duration of OTDR window <NUM>, such that there is an overlapping of clock synchronization information in each channel. As shown, such overlapping region may contain a phase detection/delay adjustment (PD/DA) window <NUM>.

As such, delay adjustments are provided to align the clock synchronization information in two channels, such that during channel selection, the two channels may contain clock synchronization information and channel selection may be performed in the PD/DA window <NUM>. It will be appreciated that each overlapping region will have the PD/DA window <NUM> to assist in channel selection.

<FIG> illustrates a detailed functional block diagram of the OSC receiver module 208a, in accordance with various embodiments discussed in the present disclosure. As shown, the OSC receiver module 208a may further include amplifiers 308a and 308b, splitters 310a and 310b, a phase detector <NUM>, a controller <NUM> and a logic processor <NUM>. The logic processor <NUM> further includes a clock data recovery (CDR) unit 316a and a logic processing unit 316b.

As previously discussed, photo detectors 302a and 302b may be configured to generate electrical signals corresponding to clock synchronization information interleaved with OTDR information at wavelengths λ<NUM> and λ<NUM>. Electrical signals are then amplified using amplifiers 308a and 308b. The amplified electrical signals may be then forwarded to delay elements 304a and 304b for delay adjustments. Delay elements 304a and 304b may provide the required delays to the electrical signals for alignment and may supply the adjusted electrical signals to splitters 310a and 310b. Splitters 310a and 310b may be configured to split the amplified electrical signals such that electrical signals may be supplied to the phase detector <NUM> and the RF switch <NUM>.

In certain embodiments phase detector <NUM> further includes a multiplier 312a, a low-pass filter 312b and an analog-to-digital converter (ADC) 312c. The phase detector <NUM> may be configured to detect analog phase difference signals between the electrical signals supplied by splitters 310a and 310b. In so doing, the multiplier 312a mixes the electrical signals and may supply the mixed electrical signals to the low-pass filter 312b. The low-pass filter 312b may then supply a voltage corresponding to the analog phase difference signals, between the electrical signals supplied by splitters 310a and 310b, to the ADC 312c. The ADC 312c converts the analog phase difference signals to digital phase difference signals and supplies the digital phase difference signals to the controller <NUM>. However, it is to be understood that the phase difference detection may be achieved by other suitable techniques, without departing from the principles presented herein.

The controller <NUM> may be configured to communicate control signals, such as, for example, phase detection and delay adjustment control signals, with the logic processing unit 316b in addition to receiving the digital phase difference signals as supplied by the phase detector <NUM>. To this end, the controller <NUM> may adjust the delays of delay elements 304a and 304b in accordance with control signals and digital phase difference signals. It will be further appreciated that in certain embodiments, phase difference detection and delay adjustment may be performed during the overlapping region of clock synchronization information in two channels.

In certain embodiments, the logic processing unit 316b may provide channel selection control signals to the RF switch <NUM>. Based on channel selection control signals, the RF switch <NUM> may select one of the two channels to provide an uninterrupted signal corresponding to clock synchronization information to the CDR unit 316a. The CDR unit 316a may further process and provide clock synchronization information to the logic processing unit 316b.

In certain situations, clock synchronization information interleaved with OTDR information at wavelengths λ<NUM>, travelling through the optical fiber 216a and clock synchronization information interleaved with OTDR information at wavelengths λ<NUM>, travelling through the optical fiber 216b might have a differential delay greater than the delay compensation capability of delay elements 304a and 304b. In certain embodiments, these differential delays may be pre-compensated at the third OSC transmitter/OTDR 206c and the fourth OSC transmitter/OTDR 206d.

To this end, in certain embodiments, the logic processing unit 316b may be configured to measure the differential delays by selecting either of the two channels carrying clock synchronization information interleaved with OTDR information and may provide the measured differential delays back to the third OSC transmitter/OTDR 206c and the fourth OSC transmitter/OTDR 206d for pre-compensation of the differential delays. As such, the third OSC transmitter/OTDR 206c and the fourth OSC transmitter/OTDR 206d may be configured to compensate for the differential delays prior to sending clock synchronization information interleaved with OTDR information over optical fibers 216a and 216b.

In certain embodiments, the third OSC transmitter/OTDR 206c and the fourth OSC transmitter/OTDR 206d may be configured to scan clock synchronization information interleaved with OTDR information at wavelengths λ<NUM>, and clock synchronization information interleaved with OTDR information at wavelengths λ<NUM> for the differential delay pre-compensations until a correlation peak is found. In such embodiments, the third OSC transmitter/OTDR 206c and the fourth OSC transmitter/OTDR 206d may be configured to pre-compensate clock synchronization information interleaved with OTDR information for differential delays without any feedback from logic processing unit 316b.

It should be understood that the third OSC transmitter/OTDR 206c and the fourth OSC transmitter/OTDR 206d may use any suitable technique to compute and pre-compensate differential delays in clock synchronization information interleaved with OTDR information at wavelengths λ<NUM>, and clock synchronization information interleaved with OTDR information at wavelengths λ<NUM>.

It should also be understood that the OSC transmitter/OTDR module 204a and the OSC receiver module 208a may be configured to operate in a similar manner as the OSC transmitter/OTDR module 204b and the OSC receiver module 208b, without departing from the principles presented herein.

<FIG> illustrates representative windows of information received by the OSC receiver modules 208a and 208b, in accordance with various embodiments discussed in the present disclosure. By way of an illustrative example, OSC may have uninterrupted windows <NUM> of <NUM> and OTDR may have an uninterrupted windows <NUM> of <NUM>. Further, each OSC window <NUM> may have <NUM> OSC frames and each OTDR window <NUM> may have <NUM> OTDR frames. Such that, each of the OSC frames 508b or OTDR frames may have duration of <NUM>.

Since, at any time, at least one of the two channels is carrying clock synchronization information uninterrupted by OTDR information, therefore clock synchronization information in the two channels may have overlapping regions for <NUM>. This <NUM> of overlap may be used by OSC receiver modules 208a and 208b to compute phase difference and provide delay adjustments to clock synchronization information interleaved with OTDR information in two channels. Further, each of the OSC frames 508b may contain an overhead window 508a.

Moreover, two channels may have identical information with time delays, the phase detector <NUM> may provide an output a voltage in accordance with the time delay between two channels. To this end, the phase detector <NUM> may use any suitable algorithm, such as, for example, hill climbing algorithm to maximize the voltage resulting in alignment of two channels. It is to be understood that the alignment may be performed repeatedly at every PD/DA window <NUM> corresponding to each OSC window <NUM>.

Once the channels are aligned, the RF switch <NUM> may perform switching between two channels to provide uninterrupted signal <NUM> corresponding to clock synchronization information. In certain embodiments, each OSC frame 508b may have a switch window 508c to assist the smooth switching operation without loss of any relevant information. All of the associated timing information may be pre-designed and managed by logic processor <NUM>.

<FIG> depicts a functional flow diagram of process <NUM> directed to a method implemented in an optical transceiver, in accordance with various embodiments of the present disclosure.

Process <NUM> commences at task block <NUM>, where the optical transceiver 202a generates a first OTDR signal and a second OTDR signal, the second OTDR signal being delayed version of the first OTDR signal. As noted above, the first OSC transmitter/OTDRs 206a and 206b generate signals associated with OTDR at wavelengths λ<NUM>, and λ<NUM>.

Process <NUM> proceeds at task block <NUM>, where the optical transceiver 202a generates a first OSC signal and a second OSC signal, the second OSC signal being delayed version of the first OSC signal. As noted above, the first OSC transmitter/OTDR 206a and the second OSC transmitter/OTDR 206b generate signals associated with OSC at wavelengths λ<NUM>, and λ<NUM> respectively.

At task block <NUM>, the optical transceiver 202a interleaves the first OSC signal with the first OTDR signal and interleaves the second OSC signal with the second OTDR signal. As discussed above, the first OSC transmitter/OTDR 206a to interleaves the signals associated with OSC and OTDR at wavelength λ<NUM> and the second OSC transmitter/OTDR 206b interleaves the signals associated with OSC and OTDR at wavelength λ<NUM>.

Process <NUM> proceeds at task block <NUM>, where the optical transceiver 202a transmits the first OSC signal interleaved with the first OTDR signal on a first optical fiber. As described above, WDM 210a receives and transmit the first OSC signal interleaved with the first OTDR signal generated at wavelengths λ<NUM>, over optical fibers 216a.

Process <NUM> advances at task block <NUM>, where the optical transceiver 202a transmits the second OSC signal interleaved with the second OTDR signal on a second optical fiber. As described above, WDM 210b receives and transmits the second OSC signal interleaved with the second OTDR signal generated at wavelengths λ<NUM>, over optical fibers 216b.

At task block <NUM>, where the optical transceiver 202a receives a third OSC signal interleaved with a third OTDR signal and a fourth OSC signal interleaved with a fourth OTDR signal. As noted above, WDMs 210a and 210b receive the third OSC signal interleaved with the third OTDR signal and the fourth OSC signal interleaved with the fourth OTDR signal generated at wavelengths λ<NUM>, and λ<NUM> transmitted by the optical transceiver 202b over optical fibers 216a and 216b respectively.

Finally at task block <NUM>, the optical transceiver 202a combines the third and fourth OSC signals to form an uninterrupted signal containing clock synchronization information. As noted above, RF switch <NUM> may make alternative switching between two channels in accordance with control signals as supplied by logic processing unit 316b. In so doing, RF switch <NUM> may provide an uninterrupted signal corresponding to clock synchronization information at wavelengths λ<NUM> and λ<NUM>.

Thus, by virtue of techniques provided by uninterrupted clock synchronization-based optical communication network <NUM>, efficient utilization of available area and power may be achieved, such that efficiency of designing ICs incorporating CMUs and multiple SerDes may be increased through the use of efficient components and design.

Claim 1:
An optical transceiver, comprising:
a first optical time domain reflectometer, OTDR, module configured to:
generate a first OTDR signal, and
generate a second OTDR signal, the second OTDR signal being a delayed version of the first OTDR signal; and
a first optical supervisory channel, OSC, transmitter configured to:
generate a first OSC signal,
generate a second OSC signal, the second OSC signal being a delayed version of the first OSC signal,
interleave the first OSC signal and the first OTDR signal, and
interleave the second OSC signal and the second OTDR signal;
a first wavelength division multiplexer, WDM, configured to transmit the first OSC signal interleaved with the first OTDR signal on a first optical fiber; and
a second WDM configured to transmit the second OSC signal interleaved with the second OTDR signal on a second optical fiber;
wherein, at any time during operation of the optical transceiver, at least one of the first and second OSC signals is present on a corresponding one of the first and second optical fibers.