Nec Corporation

Yoshitaka Yokoyama

Koji Kudo

Masayoshi Tsuji

The present invention relates to controlling wavelength switching in a plurality of nodes that are provided to increase the distance of signal transmission in inverse MUX transmission in which a high-speed line is divided into a plurality of low-speed lines for transmission. A maximum skew occurring between adjacent nodes is measured, and switching of wavelength channels is performed in one or a plurality of nodes on the basis of the measured maximum skew to keep the skew of the entire inverse MUX transmission system at or below a prescribed value. The optical communication device is provided with an NNI functional block to which high-speed lines on the transmission channel side are connected, and a UNI functional block to which low-speed lines on the client side are connected.

Optical communication method, optical communication device, and optical communication system

A small, low cost, low power-consumption optical receiver transmits signals at a high bit rate of approximately 10 Gbps over a long distance of 100 km or longer without chromatic dispersion compensation. An optical filter with a variable filtering wavelength is provided in the optical waveguide. A frequency-modulated signal light is inputted into the waveguide and transferred to the through port and the drop port thereof. The filter limits the frequency-modulated signal light to a predetermined frequency band and converts the said light to an intensity-modulated signal. The first and second converters provided at the through and drop ports to convert the first and second components of the intensity-modulated signal to electric signals, respectively. The filtering wavelength of the filter is controlled using the electric signals from the first and second converters. The input signal is regenerated from the electric signal of the second converter.

Optical receiver and optical transceiver using the same

This invention provides a technique for realizing low-cost optical signal waveform monitoring with improved realtimeness to be applied to signal quality monitoring in an actual optical transmission system, and a technique for stably controlling an optical transmitter/receiver and various compensators by means of this waveform monitoring. Opening/closing of a optical gate is controlled by means of a clock signal synchronized with an optical signal input from a photocoupler and having a period equal to the bit interval of data or N (N: a positive integer) times longer than the bit interval to allow each pulse of the optical signal for one bit of data to pass through the optical gate for only part of the time width of the gate. A photoelectric conversion element to which the optical signal transmitted through the optical gate for only part of the time width obtains an average light intensity of the input optical signal. Information on this average light intensity is output to a monitoring output section.

Apparatus and method for monitoring optical signal

A wavelength stabilized laser module is provided which is so configured as to be simplified and smaller in size and is capable of emitting semiconductor laser light whose wavelength is stablized with high accuracy. The wavelength stablized laser module includes a semiconductor laser, a substrate, a lens to convert emitted semiconductor laser light to parallel luminous flux, a first photoelectric converter to receive a part of the parallel luminous flux and to convert it to electric signals, a filter to receive a part of the parallel luminous flux, a second photoelectric converter to receive light transmitted through the filter and to convert it to electric signals, wherein a control signal to be used for stabilization obtained by computations of electric signals fed from the converters is fed back to the semiconductor laser device and/or the substrate so that said semiconductor laser is able to stably emit laser light having a reference wavelength to be used as a target for stabilization.

Wavelength stabilized laser module

A semiconductor photonic element is provided, which realize low threshold current and satisfactory characteristics in the high temperatures and/or high output operating condition. This element is comprised of (a) a semiconductor substrate; (b) a mesa structure formed on a first surface of the substrate to extend in a specific direction; the mesa structure including an active layer and a pair of p- and n-type cladding layers located respectively at top and bottom sides of the active layer, forming a double heterojunction; (c)a current-constricting structure for constricting an injection current formed at each side of the mesa structure to expose a top of the mesa structure from the current-constricting structure; the current-constricting structure comprising a first current-blocking part and a second current-blocking part; the first current-blocking part having a dielectric current-blocking layer that extends to the mesa structure; the dielectric current-blocking layer being contacted with top edges of the mesa structure; the second current-blocking part having a semiconductor current-blocking layer; and (d) a semiconductor burying layer formed to cover the mesa structure and the multilayer current-constricting structure; the semiconductor burying layer being contacted with the top of the mesa structure.

Growing community of inventors

Tokyo, Japan

Yoshitaka Yokoyama