A spatial multiplexing optical receiver includes a plurality of coherent receivers configured to coherently receive each of spatially multiplexed and transmitted signals of a plurality of modes by using continuous wave light independent for each mode as local oscillator light, a plurality of frequency offset compensators configured to perform frequency offset compensation based on a correlation between a known training signal and a signal of each mode independently for each mode, for each of the coherently received signals of the plurality of modes, and a MIMO signal processing unit configured to perform MIMO signal processing on the signals of the plurality of modes subjected to the frequency offset compensation in the frequency offset compensator.

An interference component generated because a plurality of carrier generation units and a plurality of local oscillation units are asynchronous is used as state information, a predetermined state equation for calculating posterior state information on the basis of prior state information, and a transmission data sequence are used as observation information, a Kalman filter algorithm is applied to a predetermined observation equation for calculating the observation information in a state indicated by the posterior state information on the basis of the posterior state information calculated by the state equation, a reception data sequence, and a weight matrix to calculate a posterior state estimate of the interference component, and an estimated sequence of the transmission data sequence from which the interference component has been removed is calculated on the basis of the calculated posterior state estimate.

A hollow core fiber (HCF) link is characterized by structural properties selected to support and sustain light propagation in a fundamental mode and in at least one higher-order mode. Connected to a proximal end of the HCF link, there is a mode coupler configured to couple a data signal into the fundamental mode and to couple an obfuscating signal into the at least one higher-order mode for simultaneous propagation of the data signal and the obfuscating signal on the HCF link, where the obfuscating signal substantially overlaps the data signal in spectral content. At a distal end of the HCF link, there is a mode splitter configured to split a first optical signal detected in the fundamental mode from a second optical signal detected in the at least one higher-order mode.

A method for generating frequency converted laser radiation is disclosed. The disclosure provides a method enabling generation of a frequency converted wavelength division multiplexed light source that is easy to implement at low cost. Adjustment of the center frequency and the mode spacing in a frequency converted wavelength division multiplexed light source is also disclosed. A related method of use discloses generating pump laser radiation through combination of multiple pump sources in a wavelength division multiplexed arrangement; passing the pump laser radiation through the non-linear medium of a singly resonant, single-frequency optical parametric oscillator, wherein the pump laser radiation is continuous wave or pulsed, wherein the pulse duration in the latter case is longer than the time the optical parametric oscillation requires to reach its steady state; and coupling out the non-resonant idler or signal laser radiation from the optical parametric oscillator as usable frequency converted laser radiation. Moreover, the invention relates to a laser device for carrying out the method of the invention.

A system for enabling signal penetration into a building includes first circuitry, located on an outside of the building, for receiving signals at a first frequency that experiences losses when penetrating into an interior of the building and converting the received signals at the first frequency into a first format that overcome the losses caused by penetrating into the interior of the building over a wireless communications link. The first circuitry further includes a first transceiver, implementing a first transmission chipset for RF transmissions in the first format that counteracts losses occurring when penetrating into the interior of the building, for receiving the signals at the first frequency and converting the received signals at the first frequency into the first format that overcomes the losses caused by penetrating into the interior of the building. Second circuitry, located on the interior of the building is communicatively linked with the first circuitry for receiving and transmitting the converted received signals in the first format. The second circuitry further includes a second transceiver, implementing the first transmission chipset, for receiving and transmitting the converted signals in the first format from/to the first transceiver on the exterior of the building.

Examples are disclosed that relate to the use of an optical data receiver comprising a multi-tap image sensor pixel for use in optical communications. The multi-tap pixel includes a photodetector and a plurality of taps. The optical data receiver further includes a controller comprising instructions executable for controlling the multi-tap pixel to, in a first period of time, perform a first integration on the photodetector and readout charge stored on a floating diffusion capacitor of a first tap in the plurality of taps using readout circuitry of the first tap. The controller further includes instructions executable for controlling the multi-tap pixel to, in a second period of time, perform a second integration on the photodetector and readout charge stored on a floating diffusion capacitor of a second tap in the plurality of taps using readout circuitry of the second tap.

A system for enabling signal penetration into a building includes a transceiver located on an exterior of the building for receiving signals at a first frequency transmitted from a source outside of the building. An optical bridge receives the signals at the first frequency that experiences losses when penetrating an exterior surface of the building, converts the received signals at the first frequency into a first format that overcome losses caused by penetrating an exterior surface of the building and transmits the signals through the exterior surface of the building. A WiFi transceiver located on the interior of the building and connected to the optical bridge converts between the signals in the first format and WiFi signals and for transmitting the WiFi signals to the interior of the building and receiving the WiFi signals from the interior of the building.

In order to estimate an upper limit value of a bit error rate in an optical transmission unit for an optical transmission system in which an optical sender and an optical receiver are connected each other through the optical transmission unit that utilizes plural spatial resources, and coherent detection is used, after obtaining an amplitude of each crosstalk for different spatial resource in the optical transmission unit and variance of additive white Gaussian noise in the optical transmission system, by changing a value of an independent variable in a formula of the bit error rate, a minimum value of the formula is searched for as the upper limit value of the bit error rate. The formula is represented by the amplitude of each crosstalk, the variance of the additive white Gaussian noise and the independent variable that is different from a time axis.

According to the present invention, a multiplexing optical communication system including a simple and high-efficiency optical system can be provided. The optical communication system includes an optical transmitter, a transmission path, and an optical receiver, in which the optical transmitter includes a polarized light source, a polarizing plate, a patterned retardation plate that converts light from the polarized light source into a plurality of optical vortices, a modulator, and a multiplexer.

A communications device may include a local device, a remote device, and a multi-mode optical fiber coupled between the local device and the remote device. The local device may include a local spatial optical mux/demux coupled to the multi-mode optical fiber and having first and second local optical outputs and first and second local optical inputs, and a local electro-optic E/O modulator coupled to the second local optical input. The remote device may include a remote spatial optical mux/demux coupled to the multi-mode optical fiber, and a remote E/O modulator configured to generate a modulated signal onto a first remote optical output based upon modulating the first optical carrier signal from a first remote optical input responsive to a radio frequency (RF) electrical input signal.