Methods, systems, and apparatus, including computer programs encoded on computer storage media, for performing asymmetric pulse-shaping filtering. In some implementations, a receiver comprises a detector circuit operable to receive optical signal data from an optical link. The receiver comprises a filter circuit, coupled to the detector circuit, operable to (i) filter the optical signal data according to an asymmetric filtering scheme and (ii) output the filtered optical signal data, wherein the asymmetric filtering scheme comprises utilizing a shaping filter with first criteria, the first criteria including one or more values greater than one or more values of second criteria utilized by a shaping filter at a transmitter, the transmitter communicating with the receiver.

The present disclosure relates to a chips-scale free-space optical (FSO) receiver with a wide two-dimensional field-of-view (FOV) that affords high data rate optical communication and rapid pointing and tracking (PAT) operations in an integrated design, and a method for FSO communication with PAT that supports high-speed node acquisition and network entry, and simple angle of arrival calculations.

A communication network includes a coherent optics transmitter, a coherent optics receiver, an optical transport medium operably coupling the coherent optics transmitter to the coherent optics receiver, and a coherent optics interface. The coherent optics interface includes a lineside interface portion, a clientside interface portion, and a control interface portion.

An assembly for optical to electrical power conversion including a photodiode assembly having a substrate layer and an internal side, an antireflective layer, a heterojunction buffer layer adjacent the internal side; an active area positioned adjacent the heterojunction buffer layer, a plurality of n+ electrode regions and p+ electrode regions positioned adjacent the active area, and back-contacts configured to align with the n+ and p+ electrode regions. The active area converts photons from incoming light into liberated electron hole pairs. The heterojunction buffer layer prevents electrons and holes of the liberated electron hole pairs from moving toward the substrate layer. The plurality of electrode regions are configured in an alternating pattern with gaps between each n+ and p+ electrode region. The electrode regions receive and generate electrical current from migration of the electrons and the holes, provide electrical pathways for the electrical current, and provide thermal pathways to dissipate heat.

A method includes mapping, by an optical transceiver, a received first OTU4 signal to a first FlexO frame without interleaving the first OTU4 signal into an ODUC signal prior to mapping the first OTU4 signal to the first FlexO frame. The method also includes communicating, by the optical transceiver, the first FlexO frame with the mapped first OTU4 signal to a coherent DSP over a first FOIC.

To suppress the deterioration of the characteristics of a MIMO equalizer as well as minimizing an increase in circuit size in spite of the occurrence of signal spectrum narrowing and asymmetric spectrum degradation, a wavelength-division multiplexing optical transmission system (10) according to an embodiment includes a transmitter (1) that generates one channel signal by wavelength-division multiplexing a plurality of subcarrier signals so as to overlap each other and transmits the channel signal, and a receiver (2) that separates a received channel signal into subcarrier signals, and performs equalization using an MIMO equalizer (3) including a FDE-MIMO equalizer (4) and a TDE-MIMO equalizer (5) on each of the separated subcarrier signals.

A system for generating and receiving a polarization multiplexed single sideband signal is provided, which includes a light wave generating unit connected with a signal modulating unit and configured to generate a light wave; a driving signal generating unit connected with the signal modulating unit and configured to generate a driving signal; the signal modulating unit configured to split the light wave into two orthogonal polarized light waves, and modulate the driving signal on the polarized light waves to obtain a polarization multiplexed upper sideband optical signal and a polarization multiplexed lower sideband optical signal which are coupled to output a mixed signal, the mixed signal is transmitted to a separating and converting unit to obtain electrical millimeter wave signals; the electrical millimeter wave signals are transmitted through an MIMO wireless link to a signal sampling and processing unit to be converted into digital signals for digital signal processing.

This application provides a signal processing method and apparatus, and a coherent receiver. The signal processing method includes: obtaining P real-number signals; performing at least number theoretic transform NTT processing on the P real-number signals to obtain P transform-domain first real-number signals; performing at least clock recovery on the P transform-domain first real-number signals to obtain P transform-domain second real-number signals; performing at least polarization compensation and inverse number theoretic transform INTT processing on the P transform-domain second real-number signals to obtain m time-domain complex-number signals X and m time-domain complex-number signals Y; and performing phase recovery and decoding on the m time-domain complex-number signals X and the m time-domain complex-number signals Y to obtain bit signals.

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.

An avalanche photodiode includes a silicon layer on a substrate; a germanium layer on the silicon layer; a cathode and an anode on any of the silicon layer and the germanium layer; and a plurality of contacts on the germanium layer, in addition to the cathode and the anode. The silicon layer can include a highly doped region at each end, an intrinsic doped region in a middle, and an intermediately doped region between the highly doped region at each end and the intrinsic doped region, and the cathode and the anode are each at a respective a highly doped region at each end. The germanium layer can include a plurality of highly doped regions with each including one of the plurality of contacts.