Fujitsu Corporation

Sadao Ibukuro

Yasunori Nagakubo

George Ishikawa

Satoshi Kuroyanagi

Takashi Tsuda

Setsuo Misaizu

Junichi Yoshimura

Akimitsu Miyazaki

Akihiko Hayashi

Isao Nakajima

An optical transmitter transmits a data signal developing a specific spectrum at a predetermined frequency, while an optical receiver detects amplitude information on the spectrum included in the data signal to control the received data signal to a constant amplitude on the basis of the detected amplitude information. This can provide an optical communication system and an optical receiver capable of functioning well even if the optical S/N is in a poor condition.

Optical communication system and optical receiver

There is provided a PLO device which performs high-accuracy, high-quality clock recovery. A shifted data generation part generates shifted data, and a first phase comparison part outputs first difference data. A first filter removes an alternating-current component from the first difference data and outputs a first detection voltage. A delay part delays input data for a time corresponding to half of one time slot with the use of an analog delay element and outputs delayed data. A second phase comparison part compares the phases of the input data and delayed data with each other and outputs second difference data. A second filter removes an alternating-current component from the second difference data and outputs a second detection voltage. An arithmetic section divides the first detection voltage by the second detection voltage to obtain a control voltage. A clock oscillation section outputs recovered clock based on the control voltage.

PLO device

A protection switch is configured for an input optical signal using an n&times;n optical switch. Furthermore, a signal to be added and dropped is also configured using an n&times;n optical switch. Especially, the n&times;n optical switch uses a complete group switch. Thus, a signal can be output from any input port to any output port. Therefore, a more extensible NPE can be configured at an optical signal level, and a switch is simple and less expensive. As a result, unlike the conventional technology, an NPE itself can be simple and less expensive.

Optical node system and switched connection method

In an optical modulator having an electric waveguide and an optical waveguide, a filter converts a modulating signal into a signal equalizing a frequency characteristic of an acting amount to be provided to the electric waveguide. Also, the filter approximates the frequency characteristic of the acting amount caused by a skin effect in the electric waveguide.

Optical modulator with reduced deterioration of optical waveform in high frequency band

A signal having a low frequency f is superposed on a signal having a high frequency f . The light having the frequency f is modulated and transmitted to a transmission line as a wavelength dispersion measurement light. A local oscillation light is multiplexed with the wavelength dispersion measurement light, and heterodyne-detected on a receiving side. Sideband components generated by modulating the frequency f within the heterodyne-detected wavelength dispersion measurement light are extracted by bandpass filters, and the wavelength dispersion value of the transmission line is calculated by detecting the phase difference between the sideband components.

Wavelength dispersion measuring device and a method thereof

An optical transmitter, a terminal-station apparatus having the optical transmitter, and an optical communication system employing the terminal-station apparatus. The optical transmitter comprises: a light-source unit for generating an optical signal; a monitor unit for monitoring a parameter depending on the wavelength of the optical signal; a judgment unit for determining as to whether or not the monitored parameter satisfies a predetermined condition; and a shut-off unit for shutting off the optical signal in case the monitored parameter does not satisfy the predetermined condition. By using the optical transmitter, it can be possible to prevent crosstalk from occurring between WDM (Wavelength Division Multiplexing) channels in the optical communication system.

Optical transmitter, terminal-station apparatus having the optical

In a light transmitter comprises an automatic bias control circuit which automatically controls a bias for an external modulator, a part of a light output/input signal of the external modulator is branched to detect an electrical monitor signal and a gain control signal is generated in inverse proportion to the level of the monitor signal to control the gain of the automatic bias control circuit.

Light transmitter having an automatic bias control circuit

An AGC amplifier for compensating a signal loss in a cable through which a signal having a frequency is passed, the signal loss being defined as a function of a square-root of the frequency, having a wide compensation ability and adaptable to the forming of a LSI circuit construction. The AGC amplifier includes a first amplifier (10) amplifying an input signal (IN) to be compensated at a first gain (A.sub.0), a differential circuit (40) having a constant differential coefficient defined by the frequency, and differentiating the input signal at the differential coefficient, a second amplifier (20) amplifying the differentiated signal at a second gain (A.sub.1), and an adding circuit (30) adding the amplified signals therefrom to output an output signal (OUT) in which the signal loss is compensated.

Growing community of inventors

Kawasaki, Japan

Sadao Ibukuro