Abstract: Disclosed is an optical fiber transmission system for transmitting an optical signal by DPSK modulation includes a plurality of NZ-DSF (Non-Zero Dispersion Shifted single-mode optical Fiber) transmission line blocks, each of which has N spans of a span comprising a serially connected NZ-DSF and optical repeater, and one span that includes a dispersion compensating fiber and an optical repeater. The average wavelength dispersion value of each NZ-DSF transmission line block is made non-zero.

Abstract: According to the cross phase modulation suppressing device of the present invention, the wavelength multiplexing optical signal from an optical fiber having polarization orthogonality between the adjacent channels is split for every channel and the split optical signals are led to delaying optical waveguides of different lengths by the AWG (Arrayed Waveguide Grating) connected to a second port of an optical circulator, and the split optical signals with each delay added are reflected by the Farraday mirrors in polarization states orthogonal to each other and again led to the delaying optical waveguides. The reflected lights are combined by the AWG and supplied to a third port of the optical circulator as the wavelength multiplexing optical signal with orthogonality of polarization states kept between the adjacent channels.

Abstract: A task is to provide a wavelength division multiplexing optical fiber transmission line that reduces signal deterioration caused by dispersion even in a transmission system having a high-speed transmission rate, and is suited to a long-distance transmission.

Abstract: According to the cross phase modulation suppressing device of the present invention, the wavelength multiplexing optical signal from an optical fiber having polarization orthogonality between the adjacent channels is split for every channel and the split optical signals are led to delaying optical waveguides of different lengths by the AWG (Arrayed Waveguide Grating) connected to a second port of an optical circulator, and the split optical signals with each delay added are reflected by the Farraday mirrors in polarization states orthogonal to each other and again led to the delaying optical waveguides. The reflected lights are combined by the AWG and supplied to a third port of the optical circulator as the wavelength multiplexing optical signal with orthogonality of polarization states kept between the adjacent channels.

Abstract: An optical communication receiver of this invention includes a photoelectric converter for converting an input optical signal into an electrical signal, a signal divider for dividing the electrical signal from the photoelectric converter into a plurality of signals, a clock extractor for reconstructing a clock of the photoelectrically converted input signal, phase adjusters for giving different delays to the respective signal decision timing clocks from the clock extractor or the plurality of electrical signals divided by the signal divider, a plurality of code decision units for performing code decision of the plurality of electrical signals at different timings, and an OR circuit for ORing the outputs from the plurality of code decision units. An input optical signal may be divided into signals by an optical divider before it is converted into an electrical signal.