Abstract: An audio output circuit including an input-signal generation block generating an input signal obtained by integrating a cyclic waveform and inputting the input signal to an audio amplifier at a transition from a normal operation to a power down state or at a return from the power down state to the normal operation, wherein an amplifier output terminal of the audio amplifier and an audio output unit are coupled via a capacitor.

Abstract: A signal multiplexing apparatus has an OPU/ODU processing unit putting a local protocol signal into an OPU/ODU signal, an ODTU processing unit generating an ODTU signal from the OPU/ODU signal, a read-out position detecting unit detecting a read-out position at the time that the OPU-ODU processing unit reads out the local protocol signal, and a stuff allocation controlling unit allocating a stuff control amount to be used when the OPU/ODU processing unit puts the local protocol signal into the OPU/ODU signal and a stuff control amount to be used when the ODTU processing unit generates the ODTU signal, on the basis of the read-out position detected by the read-out position detecting unit. The signal multiplexing apparatus can effectively absorb an amount of fluctuation in bit rate when asynchronously multiplexing the local protocol signal such as a 10GE signal in an optical transport network.

Abstract: 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.

Abstract: 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.

Abstract: A protection switch is configured for an input optical signal using an n×n optical switch. Furthermore, a signal to be added and dropped is also configured using an n×n optical switch. Especially, the n×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.

Abstract: A protection switch is configured for an input optical signal using an n×n optical switch. Furthermore, a signal to be added and dropped is also configured using an n×n optical switch. Especially, the n×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.

Abstract: 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.

Abstract: 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.

Abstract: A signal having a low frequency fm is superposed on a signal having a high frequency f1. The light having the frequency fs 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 fs 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.

Abstract: Disclosed herein is a device including a plurality of optical senders for generating a plurality of optical signals to which forward error correction is applied, a scrambler for polarization scrambling each of the optical signals output from the optical senders, and an optical multiplexer for wavelength division multiplexing the optical signals to obtain WDM signal light. A scrambling frequency in the scrambler is set higher than a natural frequency in the forward error correction. Accordingly, high-quality transmission is allowed without interchannel crosstalk in WDM transmission.

Abstract: 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.

Abstract: 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 SIN is in a poor condition.

Abstract: A signal having a low frequency fm is superposed on a signal having a high frequency f1. The light having the frequency fs 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 fs 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.

Abstract: A protection switch is configured for an input optical signal using an n×n optical switch. Furthermore, a signal to be added and dropped is also configured using an n×n optical switch. Especially, the n×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.

Abstract: 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.

Abstract: 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.

Abstract: 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.