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. Accordingly, probabilistic constellation shaping may be achieved over constellations of arbitrary size. In addition, relatively long codewords, may be encoded and decoded with the apparatus and method disclosed herein. Accordingly, for a fixed SNR a higher SE (more bits per symbol) can be achieved. Alternatively, for a fixed SE, a lower SNR may be sufficient. Moreover, the resulting SE may be finely tailored to a particular optical link SNR to provide data transmission rates that are higher than the low order modulation formats that would otherwise be employed for optical signals carried by such links.

Provided is an optical transceiver including a reference tunable laser module configured to generate and output light of a reference wavelength; a first general tunable laser module configured to generate and output light of a first wavelength; and a controller configured to control a tuning operation of the first wavelength of the first general tunable laser module, based on information about a relationship between the reference wavelength and the first wavelength.

Methods and apparatus for coherent transmitter calibration are provided that employ direct detection (DD) using one single photodetector (PD). The provided method and apparatus do not require hardware for coherent reception, or additional ADCs for quality control. An additional optical tone is added to a QAM optical signal that is outside the band of the QAM optical signal. The result of this is that after direct detection, there is a correlation between the real and imaginary parts, and the imaginary part can be recovered with a Hilbert transform. The estimated QAM optical signal obtained by direct detection is used to perform a transmitter factory calibration method to calibrate for one or more transmitter impairments and/or to perform in-line self-calibration.

In one embodiment, a method includes receiving at a remote network device, power and data from a central network device, wherein the power is used to power the remote network device, performing auto-negotiation with the central network device, wherein the auto-negotiation includes operating the remote network device in a low voltage mode during fault sensing of a power circuit at the remote network device, and selecting a power operating mode, wherein selecting the power operating mode includes selecting a high voltage mode if no fault is detected during the fault sensing, the high voltage mode comprising DC (direct current) pulse power. An apparatus is also disclosed herein.

There is provided an apparatus for fiber optic line continuity detection. The apparatus comprises an optical input connectable to a first optical fiber of a fiber optic line, an optical output connectable to a second optical fiber of the fiber optic line an optical interface unit configured to transmit and receive optical signals; and an optical switch having a first configuration and a second configuration. In the first configuration the optical switch is configured to pass optical signals received at the optical input to the optical interface unit and to pass optical signals received from the optical interface unit to the optical output. Whereas, in the second configuration the optical switch is configured to pass optical signals received at the optical input to the optical output.

A system may include a first module at a far end, and an optical fiber coupled to the first module. The system may also include a second module at a near end that is configured to generate and transmit instructions to the first module to control operation of the first module.

An optical transmission system including an optical transmission device and an optical reception device that receives, via an optical transmission line, a signal transmitted from the optical transmission device, the optical transmission system including a transmission-mode selection unit that selects transmission mode information in descending order of priority out of transmission mode information, which is combinations of a plurality of parameters concerning transmission performance, the transmission mode information being a plurality of kinds of the transmission mode information common to the transmission performance of the optical transmission device and the optical reception device, a signal transmission unit that transmits, to the optical reception device, a signal modulated based on the selected transmission mode information, and a signal reception unit that receives the signal and modulates the received signal based on the transmission mode information selected by the transmission-mode selection unit.

An optical receiver module which receives a first optical signal including a continuous signal or a burst signal includes: a variable optical attenuator which adjusts the first optical signal to output a second optical signal; a semiconductor optical amplifier which amplifies the second optical signal to output a third optical signal; and a controller which controls an output of at least one of the variable optical attenuator and the semiconductor optical amplifier so as to cause the semiconductor optical amplifier to operate in a region in which gain saturation of the semiconductor optical amplifier does not occur, on the basis of at least one of: a power obtained by suppressing an outside portion of the wavelength band of the first optical signal in the third optical signal; and a power obtained by extracting the outside portion of the wavelength band of the first optical signal in the third optical signal.

Methods and systems for an all-optical wafer acceptance test may include an optical transceiver on a chip, the optical transceiver comprising first, second, and third grating couplers, an interferometer comprising first and second phase modulators, a splitter, and a plurality of photodiodes. A first input optical signal may be received in the chip via the first grating coupler, where the first input optical signal may be coupled to the interferometer. An output optical signal may be coupled out of the chip via the second grating coupler for a first measurement of the interferometer. A second input optical signal may be coupled to a third grating coupler and a portion of the second input optical signal may be communicated to each of the plurality of photodiodes via the splitter. A voltage may be generated using the photodiodes based on the second input signal that may bias the first phase modulator.

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. Accordingly, probabilistic constellation shaping may be achieved over constellations of arbitrary size. In addition, relatively long codewords, may be encoded and decoded with the apparatus and method disclosed herein. Accordingly, for a fixed SNR a higher SE (more bits per symbol) can be achieved. Alternatively, for a fixed SE, a lower SNR may be sufficient. Moreover, the resulting SE may be finely tailored to a particular optical link SNR to provide data transmission rates that are higher than the low order modulation formats that would otherwise be employed for optical signals carried by such links.