Abstract: Consistent with the present disclosure, a photonic integrated circuit (PIC) is provided that has 2 N channels (N being an integer). The PIC is optically coupled to N optical fibers, such that each of N polarization multiplexed optical signals are transmitted over a respective one of the N optical fibers. In another example, each of the N optical fibers supply a respective one of N polarization multiplexed optical signals to the PIC for coherent detection and processing. A multiplexer and demultiplexer may be omitted from the PIC, such that the optical signals are not combined on the PIC. As a result, the transmitted and received optical signals incur less loss and amplified spontaneous emission (ASE) noise. In addition, optical taps may be more readily employed on the PIC to measure outputs of the lasers, such as widely tunable lasers (WTLs), without crossing waveguides.

Abstract: Consistent with the present disclosure, a photonic integrated circuit (PIC) is provided that has 2 N channels (N being an integer). The PIC is optically coupled to N optical fibers, such that each of N polarization multiplexed optical signals are transmitted over a respective one of the N optical fibers. In another example, each of the N optical fibers supply a respective one of N polarization multiplexed optical signals to the PIC for coherent detection and processing. A multiplexer and demultiplexer may be omitted from the PIC, such that the optical signals are not combined on the PIC. As a result, the transmitted and received optical signals incur less loss and amplified spontaneous emission (ASE) noise.

Abstract: Consistent with the present disclosure, a photonic integrated circuit (PIC) is provided that has 2 N channels (N being an integer). The PIC is optically coupled to N optical fibers, such that each of N polarization multiplexed optical signals are transmitted over a respective one of the N optical fibers. In another example, each of the N optical fibers supply a respective one of N polarization multiplexed optical signals to the PIC for coherent detection and processing. A multiplexer and demultiplexer may be omitted from the PIC, such that the optical signals are not combined on the PIC. As a result, the transmitted and received optical signals incur less loss and amplified spontaneous emission (ASE) noise. In addition, optical taps may be more readily employed on the PIC to measure outputs of the lasers, such as widely tunable lasers (WTLs), without crossing waveguides.

Abstract: Methods, systems, and apparatus, including an optical receiver including a laser including a gain section; and a first tunable reflector configured to output a reference signal; a first coupler formed over the substrate; a shutter variable optical attenuator formed over the substrate, the shutter variable optical attenuator including an input port configured to receive the first portion of the reference signal from the laser; and an output port configured to provide or to block, based on a control signal, the first portion of the reference signal from the laser; and a second coupler including a first port configured to receive the first portion of the reference signal from the shutter variable optical attenuator; and a second port configured to (i) provide the first portion of the reference signal from the shutter variable optical attenuator to an optical analyzer or (ii) receive a data signal from a transmitter.

Abstract: Methods, systems, and apparatus, including an optical receiver including an optical source, including a substrate; a laser provided on the substrate, the laser having first and second sides and outputting first light from the first side and second light from the second side, the first light output from the first side of the laser has a first power and the second light output from the second side has a second power; and a first modulator that receives the first light and a second modulator that receives the second light, such that the power of the first light at an input of the first modulator is substantially equal to the power of the second light at an input of the second modulator.

Abstract: Methods, systems, and apparatus, including an optical receiver including a laser including a gain section; and a first tunable reflector configured to output a reference signal; a first coupler formed over the substrate; a shutter variable optical attenuator formed over the substrate, the shutter variable optical attenuator including an input port configured to receive the first portion of the reference signal from the laser; and an output port configured to provide or to block, based on a control signal, the first portion of the reference signal from the laser; and a second coupler including a first port configured to receive the first portion of the reference signal from the shutter variable optical attenuator; and a second port configured to (i) provide the first portion of the reference signal from the shutter variable optical attenuator to an optical analyzer or (ii) receive a data signal from a transmitter.

Abstract: Methods, systems, and devices for implementing optical interface and multiplexing devices. An input optical signal is received over an input fiber by an optical interface device. A modulated optical signal and an unmodulated optical signal are demultiplexed from the input optical signal, the unmodulated optical signal is modulated based on a data signal to generate an output optical signal; and the output optical signal is transmitted over an output fiber. A modulated optical signal is received over a network connection from an optical network by an optical multiplexing device. An unmodulated optical signal is generated using a generator device; the unmodulated optical signal and a signal that includes the modulated optical signal are multiplexed using an optical multiplexer to generate an output signal; and the output signal is transmitted over an output fiber to the optical interface device.

Abstract: Consistent with an aspect of the present disclosure, optical signals are transmitted that are modulated in accordance with an 8QAM modulation format. The optical signals carry symbols of data and may be represented by a constellation in the IQ plane that includes four inner points that are symmetrically arranged about the origin, and four outer points that are uniformly distributed about the origin, but rotated relative to the inner points. The rotation is toward inner points that represent symbols for which an erroneous transition between the outer points and such inner points is more likely to result in a single bit error, instead of two bit errors, because the symbol corresponding to the outer point and the symbol corresponding to such inner point differ by just one bit. Accordingly, a binary forward error correction algorithm may be employed to correct the errored bit.

Abstract: An optical system includes an optical transmitter and a controller that determines a particular wavelength for a channel of the optical transmitter. The controller causes the optical transmitter to transmit a first optical signal with a first data sequence that is determined based on the particular wavelength, and determines a first optical power that is generated based on the first optical signal and the first data sequence. The controller causes the optical transmitter to transmit a second optical signal with a second data sequence that is determined based on the particular wavelength, and determines a second optical power that is generated based on the second optical signal and the second data sequence. The controller calculates a power difference between the first optical power and the second optical power, and causes the particular wavelength for the channel to be modified based on the calculated power difference.

Abstract: Consistent with an aspect of the present disclosure, optical signals are transmitted that are modulated in accordance with an 8QAM modulation format. The optical signals carry symbols of data and may be represented by a constellation in the IQ plane that includes four inner points that are symmetrically arranged about the origin, and four outer points that are uniformly distributed about the origin, but rotated relative to the inner points. The rotation is toward inner points that represent symbols for which an erroneous transition between the outer points and such inner points is more likely to result in a single bit error, instead of two bit errors, because the symbol corresponding to the outer point and the symbol corresponding to such inner point differ by just one bit. Accordingly, a binary forward error correction algorithm may be employed to correct the errored bit.

Abstract: Methods, systems, and apparatus, including an optical receiver including a laser including a gain section; and a first tunable reflector configured to output a reference signal; a first coupler formed over the substrate; a shutter variable optical attenuator formed over the substrate, the shutter variable optical attenuator including an input port configured to receive the first portion of the reference signal from the laser; and an output port configured to provide or to block, based on a control signal, the first portion of the reference signal from the laser; and a second coupler including a first port configured to receive the first portion of the reference signal from the shutter variable optical attenuator; and a second port configured to (i) provide the first portion of the reference signal from the shutter variable optical attenuator to an optical analyzer or (ii) receive a data signal from a transmitter.

Abstract: Methods, systems, and apparatus, including an optical receiver including an optical source, including a substrate; a laser provided on the substrate, the laser having first and second sides and outputting first light from the first side and second light from the second side, the first light output from the first side of the laser has a first power and the second light output from the second side has a second power; and a first modulator that receives the first light and a second modulator that receives the second light, such that the power of the first light at an input of the first modulator is substantially equal to the power of the second light at an input of the second modulator.

Abstract: A device receives a modulation format and a baud rate for transmission of an optical signal, and generates optical signals based on the modulation format and the baud rate. The device generates quadrature-delay-interferometer signals based on the optical signal, the modulation format, and the baud rate, and generates a particular optical signal with a particular wavelength for the modulation format and the baud rate. The device determines whether a point of the quadrature-delay-interferometer signals is associated with the particular wavelength of the particular optical signal, and sets or adjusts the particular wavelength of the particular optical signal for the modulation format and the baud rate based on whether a point of the quadrature-delay-interferometer signals is associated with the particular wavelength of the particular optical signal.

Abstract: A device may insert a set of tones into a transmitter signal at a set of frequency offsets from a set of transmitter channels associated with a set of transmitter channel wavelengths. The set of transmitter channels may include a first channel being associated with a first quantity of bandwidth and a second channel associated with a second quantity of bandwidth. The first quantity of bandwidth may be different from the second quantity of bandwidth. The device may repeatedly adjust the transmitter signal to align the set of transmitter channel wavelengths based on a set of observed responses to the set of tones, generated based on the transmitter signal passing through an optical filter, failing to match a set of expected responses.

Abstract: An optical transmitter may include one or more lasers configured to provide a primary optical signal having a primary wavelength and a secondary optical signal having a secondary wavelength to a modulator via corresponding first and second modulator inputs. The modulator may combine the primary and secondary optical signals into a combined optical signal and modulate, with an electrical signal, the combined optical signal to provide a modulated optical signal to an optical filter. The optical filter may be configured to separate, from the modulated optical signal, a modulated primary optical signal having the primary wavelength and a modulated secondary optical signal having the secondary wavelength and provide the modulated primary optical signal to a primary optical link and the modulated secondary optical signal to a secondary optical link.

Abstract: An optical system may have an optical transmitter including a digital signal processor to receive a signal channel, determine a digital signal associated with the signal channel based on information in a look-up table and based on a test tone, and output the digital signal. The optical system may further have a digital-to-analog converter to convert the digital signal to an analog signal, a laser to provide an optical signal, and a modulator to receive the optical signal and the analog signal, and modulate the optical signal based on the analog signal to form a modulated optical signal. The optical system may also have a photodiode to convert the modulated optical signal to a digital signal, a tone detector to detect the test tone based on the digital signal, and a controller to modify the information in the look-up table based on the test tone.

Abstract: An optical system includes an optical transmitter and a controller that determines a particular wavelength for a channel of the optical transmitter. The controller causes the optical transmitter to transmit a first optical signal with a first data sequence that is determined based on the particular wavelength, and determines a first optical power that is generated based on the first optical signal and the first data sequence. The controller causes the optical transmitter to transmit a second optical signal with a second data sequence that is determined based on the particular wavelength, and determines a second optical power that is generated based on the second optical signal and the second data sequence. The controller calculates a power difference between the first optical power and the second optical power, and causes the particular wavelength for the channel to be modified based on the calculated power difference.

Abstract: A device may insert a set of tones into a transmitter signal at a set of frequency offsets from a set of transmitter channels associated with a set of transmitter channel wavelengths. The set of transmitter channels may include a first channel being associated with a first quantity of bandwidth and a second channel associated with a second quantity of bandwidth. The first quantity of bandwidth may be different from the second quantity of bandwidth. The device may repeatedly adjust the transmitter signal to align the set of transmitter channel wavelengths based on a set of observed responses to the set of tones, generated based on the transmitter signal passing through an optical filter, failing to match a set of expected responses.

Abstract: An optical transmitter may include one or more lasers configured to provide a primary optical signal having a primary wavelength and a secondary optical signal having a secondary wavelength to a modulator via corresponding first and second modulator inputs. The modulator may combine the primary and secondary optical signals into a combined optical signal and modulate, with an electrical signal, the combined optical signal to provide a modulated optical signal to an optical filter. The optical filter may be configured to separate, from the modulated optical signal, a modulated primary optical signal having the primary wavelength and a modulated secondary optical signal having the secondary wavelength and provide the modulated primary optical signal to a primary optical link and the modulated secondary optical signal to a secondary optical link.

Abstract: An optical system may include a polarization beam splitter having an input that receives multiple optical signals, a first output and a second output. The first output may provide components of the multiple optical signals having a first polarization. The second output may provide components of the multiple optical signals having a second polarization. The optical system may include a rotator having an input that receives the components to rotate the first polarization such that each of the components has the second polarization, and an output to supply components as rotated components. The optical system may also include an optical circuit including a substrate. The rotator may be separate from the substrate. The optical circuit may include an optical demultiplexer circuit provided on the substrate to receive the rotated components and the components.