Abstract: Techniques for efficiently utilize the available bandwidth in a communication network are described. One example implementation includes a method of optical communication including receiving bandwidth requests from multiple network devices in an optical network, receiving communication capability information about the multiple network devices, generating a transmission schedule that specifies transmissions in the optical network in multiple time slots with a corresponding modulation format, and transmitting and/or receiving data based on the transmission schedule.

Abstract: The differences in the power received from multiple optical network units connected to an optical hub may exceed an allowable dynamic range. The dynamic range may be reduced by determining the power received at the optical hub from each optical network unit and adjusting the power transmitted from one or more optical network units to reduce the overall dynamic range. For each optical network unit, the hub may determine the received optical power in an upstream signal from the optical network unit and receive a digital representation of the transmitted power. The hub may determine to adjust the optical power sent from one or more of the optical network units to reduce the dynamic range. The adjustments to the optical powers at the optical network units may be performed by sending commands from the optical hub to each adjusted optical network unit via a downstream signal.

Abstract: A method of digital communication is described. The method includes generating a first orthogonal frequency division multiplexed (OFDM) signal from a first portion of information bits received at the communication apparatus, generating a second OFDM signal from a second portion of information bits received at the communication apparatus, generating a first input for a modulator using the first OFDM signal and the second OFDM signal, generating a second input for the modulator using the second OFDM signal and the second OFDM signal, and operating the modulator to produce a modulated signal from the first input and the second input.

Abstract: At a transmitter-side in an optical communication network, pulse amplitude modulation optical signals to be transmitted are pre-compensated using a chromatic dispersion pre-compensation stage and a device non-linearity pre-compensation stage. The non-linearity pre-compensation may be achieved by using look-up tables that are built based on messages exchanged between the transmitter and a target receiver using known symbol patterns.

Abstract: Duo-binary encoding is used for encoding I and Q data prior to performing orthogonal frequency division multiplexing based transmission using discrete Fourier transform spreading (DFT-S). Advantageously, duo-binary encoding improves robustness of the encoded signal to inter symbol interference, making the degradation caused by the subsequent DFT-S stage less susceptible to reduction in bit error rate performance.

Abstract: The filter estimate produced by post-equalization processing of an optical signal at a receiver is used to generate pre-equalizer filter coefficients that are communicated back to the source of the optical signal for performing pre-equalization. In one advantageous aspect, the already existing post-equalization modules of an optical receive equipment can thus be used to produce, in addition, a pre-equalizer filter for use by the source side.

Abstract: Disclosed systems, methods, and computer program products enable high symbol-rate optical Nyquist signal generation with roll-off factors approaching zero by combining digital and all-optical methods. The combined digital and all-optical methods utilize all-optical sine-shaped pulse generation and orthogonal time-division multiplexing with quadrature amplitude modulation using digital Nyquist signals. Disclosed embodiments exhibit inter-channel-interference penalties that are less than 0.5-dB for both 75-GBaud and 125-GBaud optical Nyquist signals, in contrast to conventional signals generated using rectangular waveform driving signals that exhibit penalties greater than 2.5-dB and 1.5-dB for 75-GBaud and 125-GBaud signals, respectively. The disclosed embodiments, therefore, enable significant improvement over conventional systems by reducing inter-channel-interference penalties caused by excess modulation induced bandwidth.

Abstract: Systems, devices and techniques for processing received QPSK modulated optical signals include sampling the received signal at twice the baud rate, thereby producing samples that are then processed as 9-QAM symbols using a decision directed least squares optimization method. A third stage of channel equalization is filtering performs channel equalization to mitigate linear filtering effects along the transmission link. Data bits are then recovered from the resulting symbol estimates. The received optical signal may also include dual polarized signals for increased bandwidth capacity.

Abstract: The filter estimate produced by post-equalization processing of an optical signal at a receiver is used to generate pre-equalizer filter coefficients that are communicated back to the source of the optical signal for performing pre-equalization. In one advantageous aspect, the already existing post-equalization modules of an optical receive equipment can thus be used to produce, in addition, a pre-equalizer filter for use by the source side.

Abstract: Duo-binary encoding is used for encoding I and Q data prior to performing orthogonal frequency division multiplexing based transmission using discrete Fourier transform spreading (DFT-S). Advantageously, duo-binary encoding improves robustness of the encoded signal to inter symbol interference, making the degradation caused by the subsequent DFT-S stage less susceptible to reduction in bit error rate performance.

Abstract: An optical transmitter multiplexes multiple optical channels for transmission over an optical communication medium. The spectrum of modulated signal in each optical channel is lowpass filtered in the electrical (digital) domain at half the channel baud rate such that super Nyquist signal multiplexing can be achieved in the optical domain without having to perform optical filtering. An optical coupler may be used to multiplex the multiple optical channels.

Abstract: Systems, devices and techniques for processing received QPSK modulated optical signals include sampling the received signal at twice the baud rate, thereby producing samples that are then processed as 9-QAM symbols using a decision directed least squares optimization method. A third stage of channel equalization is filtering performs channel equalization to mitigate linear filtering effects along the transmission link. Data bits are then recovered from the resulting symbol estimates. The received optical signal may also include dual polarized signals for increased bandwidth capacity.

Abstract: Systems, devices and techniques for processing an optical signal transmitted from a source over a transmission medium having a length L and performing compensation of non-linear distortions include formulating the compensation as a digital back propagation algorithm by logically dividing the length L into N steps and compensating non-linear distortions for each step as a function of an attenuation adjusting constant parameter that can be selected from a range between 0.3 and 0.7.

Abstract: Systems, devices and techniques for processing an optical signal transmitted from a source over a transmission medium having a length L and performing compensation of non-linear distortions include formulating the compensation as a digital back propagation algorithm by logically dividing the length L into N steps and compensating non-linear distortions for each step as a function of an attenuation adjusting constant parameter that can be selected from a range between 0.3 and 0.7.