摘要:
The semiconductor device of this invention consists at least of a laminate of a semi-insulating or p-type first semiconductor layer having a forbidden band width E.sub.g1, an undoped or p.sup.- -type second semiconductor layer having a forbidden band width E.sub.g2 and an n-type third semiconductor layer having forbidden band width E.sub.g3. The laminate is deposited on a predetermined semiconductor substrate and the forbidden band width has the relation E.sub.g2
摘要:
This invention consists in improvements in a buried-heterostructure laser with buried optical guide, and facilitates the oscillation of the laser in the fundamental mode thereof and also enhances the available percentage of production of the laser. An active layer and an optical guide layer are sandwiched between two cladding layers, to form an optical confinement region. The width of the semiconductor material assembly varies in the direction of the stacked layers, and the narrowest part thereof is located on a side opposite to the optical guide layer with reference to the position of the active layer. The side surface of said semiconductor material assembly parallel to the traveling direction of laser radiation is buried by a burying layer.
摘要:
A digital coherent receiving apparatus includes a first oscillator for outputting a local light signal of a fixed frequency, a hybrid unit mixing the local light signal with a light signal received by a receiver, a second oscillator for outputting a sampling signal of a sampling frequency, a converter for converting the mixed light signal into digital signal synchronizing with the sampling signal, a waveform adjuster for adjusting a waveform distortion of the converted digital signal, a phase adjustor for adjusting a phase of the digital signal adjusted by the waveform adjustor, a demodulator for demodulating the digital signal adjusted by the phase adjuster, and a phase detector for detecting a phase of the digital signal adjusted by the phase adjuster, and a control signal output unit for outputting a frequency control signal on the basis of the detected phase signal to the second oscillator.
摘要:
An optical transmission system, where in an optical transmitter a detection bit having a specific pattern set according to the number of bits to be transmitted within one symbol time, is imparted with respect to a transmission signal in which transmission information has been encoded according to a preset format, and an optical signal generated by modulating light according to the transmission signal is transmitted to a transmission line. In an optical receiver, logic inversion or bit swap of received data is detected and compensated by using the detection bit included in the received signal, a decoding process of the compensated received signal is executed. As a result, when an optical signal capable of transmitting multi-bit information within one symbol time is transferred, it is possible to realize excellent transmission characteristics, by reliably compensating an error in received data caused by the modulation format or the multiplex system of the optical signal.
摘要:
The optical transmitter includes a light source; a signal processor; an optical modulator that modulates output light from the light source in accordance with a transmitting signal subjected to digital signal processing in the signal processor and outputs the modulated light as a light signal to a transmission path; and a control circuit that controls a carrier-wave frequency of the light signal output from the optical modulator, the signal processor including a mapping circuit that maps the transmitting signal to electric-field information according to a modulating scheme, and a phase rotating circuit that provides a phase rotation having a constant cycle to an electric-field phase of the electric-field information to which the mapping circuit maps the transmitting signal, the control circuit controlling the cycle of the phase rotation that the phase rotating circuit provides and thereby controlling the carrier-wave frequency of the light signal output from the optical modulator.
摘要:
An apparatus includes a first estimator that estimates a signal quality based on an error correction number of an electrical signal obtained by photoelectrically converting a received optical signal; a second estimator that estimates a signal quality from which the influence of nonlinear effects is removed based on signals upstream and downstream of an identification calculator identifying the electrical signal; and a calculator that calculates the difference between the signal qualities estimated by the first and second estimators to calculate the amount of nonlinear effects.
摘要:
A digital coherent optical receiver provided with a 90-degree optical hybrid circuit for detecting an in-phase signal and a quadrature signal of an input optical signal, includes first through fourth circuits. The first circuit calculates a square of a sum of the in-phase signal and the quadrature signal. The second circuit subtracts a squared value of the in-phase signal and a squared value of the quadrature signal from the calculation result of the first circuit. The third circuit detects a phase error of the 90-degree optical hybrid circuit based on the calculation result of the second circuit. The fourth circuit corrects at least one of the in-phase signal and the quadrature signal according to the phase error detected by the third circuit.
摘要:
An optical transmitter is provided for transmitting a wavelength multiplexed signal comprising an intensity modulation optical signal and a phase modulation optical signal through a transmission line. The optical transmitter includes a bit time difference given signal generator for generating at least two optical signals having a bit time difference therebetween, from the wavelength multiplexed signal. The optical transmitter further includes a wavelength multiplexed signal output unit to which at least two optical signals are input from the bit time difference given signal generator, and which generates and outputs a wavelength multiplexed signal in which the bit time difference was given between the phase modulation optical signal and the phase modulation optical signal.
摘要:
A polarization multiplexing and transmitting apparatus generates polarization multiplexed light by multiplexing modulated signal components that having varying intensities and are in polarization states orthogonal to each other. The polarization multiplexing and transmitting apparatus includes a converting unit that converts light generated by a light source into signal components having a varying intensity synchronized with a clock signal input thereto and a varying intensity inversely synchronized with the clock signal, respectively; a modulating unit that modulates the signal components, respectively; and a polarization adjusting unit that orthogonalizes polarization states of the signal components.
摘要:
A digital coherent receiving apparatus includes a first oscillator for outputting a local light signal of a fixed frequency, a hybrid unit mixing the local light signal with a light signal received by a receiver, a second oscillator for outputting a sampling signal of a sampling frequency, a converter for converting the mixed light signal into digital signal synchronizing with the sampling signal, a waveform adjuster for adjusting a waveform distortion of the converted digital signal, a phase adjustor for adjusting a phase of the digital signal adjusted by the waveform adjustor, a demodulator for demodulating the digital signal adjusted by the phase adjuster, and a phase detector for detecting a phase of the digital signal adjusted by the phase adjuster, and a control signal output unit for outputting a frequency control signal on the basis of the detected phase signal to the second oscillator.