Abstract: A printed circuit board including a set of five layers encompassing a breakout area is described. The set includes a first ground layer, a first signal layer having a first conductive layer within the breakout area, a second ground layer having conductive material, a second signal layer having a second conductive layer within the breakout area, and a third ground layer. The second ground layer having a void forming a differential pair being two parallel traces, and being separated into a first portion positioned within the breakout area and a second portion outside of the breakout area. The differential pair having a first width and a first spacing within the breakout area and a second width and second spacing outside of the breakout area, with the second width greater than the first width. The first and second conductive layers forming a first ground plane and a second ground plane.

Abstract: A photonic integrated circuit is provided that may include a substrate; one or more optical sources, on the substrate, to output light associated with a corresponding one or more optical signals; one or more waveguides connected to the one or more optical sources; a multiplexer connected to the one or more waveguides; and one or more light absorptive structures, located on the substrate adjacent to one of the one or more optical sources, one of the one or more waveguides, and/or the multiplexer, to absorb a portion of the light associated with at least one of the corresponding one or more optical signals.

Abstract: An example apparatus includes an optical transmitter, an optical splitter, lenses, and mirrors. The optical splitter has an input and several outputs. The input of the optical splitter is optically coupled to the transmitter, such that each of the outputs of the optical splitter is operable to supply a corresponding one of a plurality of modulated optical signals, each of which includes a plurality of optical subcarriers. Each of the lenses is optically coupled to a respective one of the outputs of the optical splitter. Each of the lenses is operable to receive a corresponding one of the modulated optical signals. Each of the mirrors is optically coupled to a corresponding one of the lenses, such that each of the mirrors is operable to direct a respective one of the modulated optical signals for transmission through free space.

Abstract: Consistent with the present disclosure, an encoder circuit is provided at a transmit side of an optical fiber link that maps an input sequence of bits of fixed length k a sequence of symbols of a codeword of length n, such that the symbols of the codeword define a predetermined transmission probability distribution. Preferably, each symbol of the codeword is generated during a corresponding clock cycle, such that after n clock cycles, a complete codeword corresponding to the input bit sequence is output. On a receive end of the link, a decoder is provided that outputs the k-bit sequence every n clock cycles. Accordingly, buffers need not be provided at the output of the encoder and the input of the decoder, such that processing of the input sequence, codewords, and output sequence may be achieved efficiently without large buffers and complicated circuitry. Moreover, the input sequence, with any binary alphabet may be matched to a desired output distribution with any arbitrary alphabet.

Abstract: Consistent the present disclosure, a network or system is provided in which a hub or primary node may communication with a plurality of leaf or secondary nodes. The hub node may operate or have a capacity that may be greater than that of the leaf nodes. Accordingly, relatively inexpensive leaf nodes may be deployed that receive data carrying optical signals from and supply data carrying optical signals to the hub node. One or more connections may couple each leaf node to the hub node, whereby each connection may include one or more spans or segments of optical fibers, optical amplifiers, and optical add/drop multiplexer, for example. Consistent with an aspect of the present disclosure, optical subcarriers may be transmitted over such connections. The subcarriers may be generated by a combination of a laser and a modulator, such that multiple lasers and modulators are not required, and costs may be reduced.

Abstract: An example system includes a plurality of hub transceivers and a plurality of edge transceivers. A first hub transceiver is operable to determine that the first hub transceiver is configured to assign a first subset of network resources to a first subset of the edge transceivers for communication over an optical communications network, and determine that a second hub transceiver is configured to assign a second subset of network resources to a second subset of the edge transceivers for communication over the optical communications network. The first hub transceiver is also operable to determine that the first subset of network resources overlaps the second subset of network resources, and in response, transmit a notification of the overlap to a control module of the optical communications network.

Abstract: A system and method is disclosed in which circuitry of a first controller of a first node on a first path within a transport network receives a first signal indicating a failure within the first path from a second controller. The first node is an end node of the first path. A first client signal failure clear signal is received from a second node upstream of the first node on the first path. The first client signal failure clear signal indicates that a non-restorable fault has been resolved such that the first path can be considered for carrying data traffic. The non-restorable fault is a failure at the source. Subsequent to receiving the first signal indicating the failure within the first path, a backward defect indication clear signal is transmitted to the second node, the backward defect indication clear signal indicating an absence of a failure in the first path.

Abstract: Joint estimation of the framer index and the frequency offset in an optical communication system are described among various other features. A transmitter can transmit data frames using pilot and framer symbols. A receiver can estimate the framer index and frequency offset using the pilot and framer symbols, and identify the beginning of a header portion of a data frame. By identifying the beginning of the header portion of a data frame, the receiver can synchronize, with less error, the data transmitted by the transmitter and the data it received. To further improve the framer index estimation, a lock indicator signal can be generated to signal to other receiver components that the estimated framer indices are reliable. The receiver can determine frequency offset and additional framer index estimations with increased reliability when performed after the lock indicator signal is generated.

Abstract: Joint estimation of the framer index and the frequency offset in a optical communication system are described among various other features. A transmitter can transmit data frames using pilot and framer symbols. A receiver can estimate the framer index and frequency offset using the pilot and framer symbols, and identify the beginning of a header portion of a data frame. The estimation can be performed to compensate for delays such as half-symbol delays and differential group delays. By identifying the beginning of the header portion of a data frame while compensating for certain delays, the receiver can synchronize, with less error, the data transmitted by the transmitter and the data it received.

Abstract: Optical networks, transponders and single-laser coherent transceiver are described. The single-laser coherent transceiver includes a wavelength source, a transmitter and a receiver. The wavelength source is tuned to supply a first optical signal having a first wavelength. The transmitter receives the first optical signal and encodes client data into the first optical signal to generate a second optical signal. The receiver receives the first optical signal from the wavelength source and a fraction of the second optical signal.

Abstract: Consistent with the present disclosure independent phase and frequency clock recovery on each SC. Both leaf and hub perform digital clock recovery on each SC by increasing the Rx-ADC sampling rate by a few ppm (˜16 ppm), and using a delay compensating element, together with gapped clocks. The gaps and delay compensating elements are independent on each SC. The delay element is performed using the frequency domain DSP engine, where the frequency domain equalizer coefficients are modified with a delay compensating element Thus, each SC can have its own fine timing frequency and timing phase tuning, and fine tracking of its own jitter. When the delay compensating element, which, for example, may include a finite impulse response (FIR) filter, reaches the end of its range, a clock gap equal to an integer number of symbols is performed. The delay element can be reset by the same number of symbols providing continuous phase interpolation.

Abstract: An optical network and a method are described. In the method, an orchestrator of an optical communication system receives an operation to execute, the operation being to activate or deactivate a service within a transmission signal of the optical communication system, the optical communication system having a span and an amplifier coupled to and supplying optical signals into each span. Network status data for each span within the optical communication system is retrieved, and the list of operations is analyzed with the network status data including existing data traffic on the fiber optic line to select a subset of the list of operations to execute that maintains the transmission signal below a bit error rate threshold. The orchestrator issues one or more signals to cause the one or more service within the subset of the list of operations to be activated or deactivated on the optical communication system.

Abstract: An example system includes a hub transceiver and a plurality of edge transceivers. The hub transceiver is operable to transmit, over a first communications channel, a first message to each of the edge transceivers concurrently, including an indication of available network resources on an optical communications network. Each of the edge transceiver is operable to transmit, transmit, over a second communications channel, a respective second message to the hub transceiver including an indication of a respective subset of the available network resources selected by the edge transceiver for use in communicating over the optical communications network. Further, the edge transceiver is operable to receive, from the hub transceiver, a third message acknowledging receipt of a selection and a fourth message confirming an assignment of the selected subset of the available network resources to the edge transceiver.

Abstract: An example method is performed by a terrestrial control system communicatively coupled to a constellation of satellites. According to the method, instructions are transmitted to a first satellite of the constellation to transmit a plurality of first groups of optical subcarriers to a plurality of second satellites of the constellation via free-space optical communication. The first groups of optical subcarriers carry first data and each of the first groups of optical subcarriers is associated, respectively, with a different communications module of the second satellites. Further, instructions are transmitted to the second satellites to transmit a plurality of second optical subcarriers to the first satellite via free-space optical communication. The second groups of optical subcarriers carry second data and each of the second groups of optical subcarriers is associated, respectively, with a different communications module of the second satellites.

Abstract: An example apparatus includes a first communications module having a first transceiver. The first communications module is operable to transmit, using the first transceiver, a plurality of first groups of optical subcarriers to a plurality of second communications modules via free-space optical communication. The first groups of optical subcarriers carry first data, and each of the first groups of optical subcarriers is associated, respectively, with a different one of the second communications modules. The first communications module is also operable to receive, using the first transceiver, plurality of second groups of optical subcarriers from the second communications modules via free-space optical communication. The second groups of optical subcarriers carry second data and each of the second groups of optical subcarriers is associated, respectively, with a different one of the second communications modules.

Abstract: Techniques are described for implementing an out-of-band communication channel used to exchange control channel information in sub-carrier-based optical communication systems. In an example implementation, an optical communication system includes a primary transceiver, a component, and secondary transceivers. The primary transceiver is operable to supply first optical subcarriers to an optical communication path, the first optical subcarriers being amplitude modulated at a first frequency to carry first control information and amplitude modulated at a second frequency to carry second control information. The component is operable to be coupled to the optical communication path and includes circuitry operable to detect the first control information. The secondary transceivers are coupled to a terminal end of the optical communication path. At least one of the secondary transceivers is operable to detect the second control information and block the first control information.

Abstract: Techniques for calculation of CRC values for very large Ethernet packets in a quick manner are disclosed. Portions of CRC values are calculated each frame and are combined to arrive at a final CRC value for the frame. The CRC values for each frame are also combined to arrive at the final value for the packet. The use of the zero-wheeling function allows for each CRC value calculation to be a calculation of a limited set of data (e.g., one chunk of a frame), which allows such calculations to be completed quickly.

Abstract: Consistent with the present disclosure, an encoder circuit is provided at a transmit side of an optical fiber link that maps an input sequence of bits of fixed length k a sequence of symbols of a codeword of length n, such that the symbols of the codeword define a predetermined transmission probability distribution. Preferably, each symbol of the codeword is generated during a corresponding clock cycle, such that after n clock cycles, a complete codeword corresponding to the input bit sequence is output. On a receive end of the link, a decoder is provided that outputs the k-bit sequence every n clock cycles. Accordingly, buffers need not be provided at the output of the encoder and the input of the decoder, such that processing of the input sequence, codewords, and output sequence may be achieved efficiently without large buffers and complicated circuitry. Moreover, the input sequence, with any binary alphabet may be matched to a desired output distribution with any arbitrary alphabet.

Abstract: Techniques are described for implementing an out-of-band communication channel used to exchange control channel information in sub-carrier-based optical communication systems. In an example implementation, an apparatus includes laser operable to supply an optical signal, a digital signal processor operable to supply digital signals, a digital to analog circuitry operable to provide analog signals based on the digital signals, and driver circuitry is coupled to the digital to analog circuitry and operable to supply at least one drive signal. The apparatus also includes a modulator operable to receive said at least one drive signal, modulate the optical signal based on said at least one drive signal to provide a plurality of optical subcarriers, amplitude modulate the plurality of optical subcarriers at a first frequency to carry first control information, and modulate the plurality of subcarriers at a second frequency to carry second control information.

Abstract: Optical network systems are disclosed, including a system comprising a transmitter including a digital signal processor operable to receive a plurality of independent data streams and output a plurality of digital signals based on the plurality of independent data streams, digital-to-analog circuitry operable to supply a plurality of analog signals based on the plurality of digital signals, a laser operable to supply an optical signal, a modulator operable to receive the optical signal and supply a modulated optical signal based on the plurality of analog signals, including a plurality of optical subcarriers, each of which being associated with a corresponding one of the plurality of independent data streams, a first one of the plurality of optical subcarriers having a first spectral width and a second one of the plurality of optical subcarriers having a second spectral width different than the first spectral width; and a first and a second receiver.