A multi-level optical signal is sampled to generate an eye diagram. The signal can be adjusted when eyes in the eye diagram have different heights. More specifically, a first value is determined, and the height of a first eye is adjusted using the first value. The first value is multiplied by a stored factor to produce a second value, and the height of a second eye is adjusted using the second value, and so on for other eyes. As a result, eye heights are the same. Similarly, optical power levels of the signal can be adjusted when the levels are not equally spaced. As a result, the optical power levels are equally spaced.

An optical amplifying fiber includes: at least one single core portion doped with a rare-earth element; an inner cladding portion configured to enclose the at least one core portion, the inner cladding portion having a lower refractive index than maximum refractive index of each core portion; and an outer cladding portion configured to enclose the inner cladding portion, the outer cladding portion having a lower refractive index than refractive index of the inner cladding portion, wherein the inner cladding portion includes a plurality of air bubbles.

Systems and methods include an optical switch system which provides a combination of .Math.LED arrays, PDs, imaging fiber cables, and crosspoint switch on a single chip. The system includes one or more input ports with each inputport configured to connect to an inputfiber bundle. The system additionally includes one or more output ports with each output port configured to connect to an outputfiber cable, wherein each of the inputfiber bundle and the outputfiber cable include a plurality of fiber cores. An electrical crosspoint switch is connected to the one or more input ports and the one or more output ports, wherein the electrical crosspoint switch is configured to connect a given input port to a corresponding output port, including all signals in the input fiber cable to the corresponding output fiber cable.

A wavelength division multiplexer/demultiplexer, a photonic integrated chip, and an optical module are provided. The wavelength division multiplexer/demultiplexer includes a substrate, a bus waveguide provided on the substrate, and at least two wavelength division multiplexing/demultiplexing units provided on the bus waveguide. Each of the at least two wavelength division multiplexing/demultiplexing units includes a mode multiplexer and an asymmetric Bragg grating. The mode multiplexer includes a first port, a second port, and a third port. The third port is connected to the asymmetric Bragg grating, so as to input a light in a TE1 mode or a higher-order mode to the asymmetric Bragg grating. The asymmetric Bragg grating transmits light containing wavelengths other than a wavelength λi. A grating period of the asymmetric Bragg grating and the wavelength λi satisfy a resonance condition.

A wavelength division multiplexer/demultiplexer, a photonic integrated chip, and an optical module are provided. The wavelength division multiplexer/demultiplexer includes a substrate, a bus waveguide provided on the substrate, and at least two wavelength division multiplexing/demultiplexing units provided on the bus waveguide. Each of the at least two wavelength division multiplexing/demultiplexing units includes a mode multiplexer and an asymmetric Bragg grating. The mode multiplexer includes a first port, a second port, and a third port. The third port is connected to the asymmetric Bragg grating, so as to input a light in a TE1 mode or a higher-order mode to the asymmetric Bragg grating. The asymmetric Bragg grating transmits light containing wavelengths other than a wavelength λi. A grating period of the asymmetric Bragg grating and the wavelength λi satisfy a resonance condition.

A signal receiving apparatus includes at least one signal separating apparatus that separates a specific signal from a plurality of received signals. Each of the at least one signal separating apparatus includes a spatial filtering unit that separates at least one equalized signal and a decision signal outputting unit that generates a first decision signal by deciding the equalized signal and outputs the generated first decision signal. The spatial filtering unit separates the at least one equalized signal by multiplying at least the plurality of received signals among the plurality of received signals and either the first decision signal output from the decision signal outputting unit or a second decision signal output from another signal separating apparatus by predetermined weighting coefficients.

A signal receiving apparatus includes at least one signal separating apparatus that separates a specific signal from a plurality of received signals. Each of the at least one signal separating apparatus includes a spatial filtering unit that separates at least one equalized signal and a decision signal outputting unit that generates a first decision signal by deciding the equalized signal and outputs the generated first decision signal. The spatial filtering unit separates the at least one equalized signal by multiplying at least the plurality of received signals among the plurality of received signals and either the first decision signal output from the decision signal outputting unit or a second decision signal output from another signal separating apparatus by predetermined weighting coefficients.

The signal detection device includes the signal detection unit that derives the estimation vector of the transmission signal vector,

the first conversion unit that converts the estimation vector of the transmission signal vector to the estimation vector of the transmission signal vector based on the reduced basis, the first determination unit that converts the estimation vector of the transmission signal vector based on the reduced basis to the determination value vector of the transmission signal vector, the first update unit that updates the separation matrix, the second conversion unit that converts the first error signal vector to the second error signal vector based on the reduced basis, the second update unit that updates the error covariance matrix based on the reduced basis, the second determination unit that determines whether or not the predetermined condition is satisfied, and a third update unit that updates the unimodular matrix, the inverse matrix of the unimodular matrix, and the error covariance matrix based on the reduced basis when it is determined that the predetermined condition is established.

The signal detection device includes the signal detection unit that derives the estimation vector of the transmission signal vector,

the first conversion unit that converts the estimation vector of the transmission signal vector to the estimation vector of the transmission signal vector based on the reduced basis, the first determination unit that converts the estimation vector of the transmission signal vector based on the reduced basis to the determination value vector of the transmission signal vector, the first update unit that updates the separation matrix, the second conversion unit that converts the first error signal vector to the second error signal vector based on the reduced basis, the second update unit that updates the error covariance matrix based on the reduced basis, the second determination unit that determines whether or not the predetermined condition is satisfied, and a third update unit that updates the unimodular matrix, the inverse matrix of the unimodular matrix, and the error covariance matrix based on the reduced basis when it is determined that the predetermined condition is established.

Optical communication system communicates between an array of originating tiles and an array of terminating tiles. Each array is associated with a lenslet array, such as a two-layer array. Each originating tile has an array and each terminating tile has an array of transceivers. Each tile is associated with a common lenslet or lenslet pair. A beamlet from a representative originating transceiver passes through the lenslet pair adjacent to its tile via an originating Fourier transform element, collimating optics, and a terminating Fourier transform element. The beam then passes through the lenslet pair adjacent to the tile containing the terminating transceiver associated with the representative originating transceiver, and is focused onto that receiver by that lenslet pair. Originating and/or terminating arrays of multicore fibers may be used between the originating transceivers and the originating Fourier transform element and/or between the terminating Fourier transform element and the terminating transceivers.