Abstract: A wavelength division multiplexing optical transmission apparatus for transmitting wavelength division multiplexing optical signals, the apparatus including a plurality of optical transmitting units outputting optical signals having a different wavelength from each other, a plurality of optical intensity modulating units intensity-modulating the optical signals, and a wavelength multiplexing unit multiplexing the optical signals. The plurality of optical intensity modulating units sets the amount of wavelength chirp adapting to each wavelength of the optical signals for the optical signals outputted from each of the plurality of optical transmitting units, and the wavelength multiplexing unit multiplexes the optical signals having the amount of wavelength chirp set respectively and then outputs the multiplexed optical signals.

Abstract: A wavelength division multiplexing optical transmission apparatus for transmitting wavelength division multiplexing optical signals, the apparatus including a plurality of optical transmitting units outputting optical signals having a different wavelength from each other, a plurality of optical intensity modulating units intensity-modulating the optical signals, and a wavelength multiplexing unit multiplexing the optical signals. The plurality of optical intensity modulating units sets the amount of wavelength chirp adapting to each wavelength of the optical signals for the optical signals outputted from each of the plurality of optical transmitting units, and the wavelength multiplexing unit multiplexes the optical signals having the amount of wavelength chirp set respectively and then outputs the multiplexed optical signals.

Abstract: A transmission device includes a change-point counter counting, for a predetermined time interval, a number af change points in code included in an input digital signal for outputting a count result. A transmission rate identification circuit determines a transmission rate of the input digital signal based on the count result. The input digital signal includes an STM-N (Synchronous Transfer Mode: N is a positive integer) signal. The time interval is a value in a range from a time equivalent to three bytes of STM-4 to a time equivalent to N×10 bytes.

Abstract: A light source in which a signal light having a wavelength outside a normal tolerance is not supplied to the outside of the light source. A temperature control circuit controls an optical switch so that the signal light outputted from a laser diode (LD) module is not supplied to the outside unless a temperature of the LD comes to be within the normal tolerance. An LD-driving circuit supplies a current to the LD in the LD module, and controls a light power outputted from the LD.

Abstract: In an optical transmitter, light outputs with different wavelengths are emitted from a plurality of light sources by a plurality of driving circuits, respectively. An optical switch control circuit controls an optical switch in response an input connection instruction such that an optional one of a plurality of input ports is connected to an optional one of a plurality of output ports to pass the light output from the optional input port to the optional output port. A plurality of modulator driving circuits drive a plurality of optical modulators in accordance with a plurality of data signals such that the light outputs from the output ports are optically modulated by the plurality of optical modulators, respectively.

Abstract: In an optical receiver including an avalanche photodiode (APD), a monitor circuit monitors the operating point of a preamplifier. A bias control circuit usually transfers a control signal received from an AGC (Automatic Gain Control) control circuit to an APD bias circuit. When the value being monitored by the monitor circuit exceeds a preselected level, the bias control circuit controls the APD bias circuit such that the above value coincides with the preselected level. The various sections of the receiver are free from damage ascribable to an increase in the photocurrent of the APD.

Abstract: It is the object of the invention to provide a lightwave transmitter, in which the lightwave surge is not generated, as soon as the input lightwave signal is down momentarily. A signal down detecting circuit monitors a data signal and a clock signal, and generates a down detecting signal, as soon as one down of the data and clock signals is detected, and till a predetermined period of time, which is longer than a mean life time of carriers on excitation level of Er-doped optical fiber, has passed. While the down detecting signal is supplied, an output power control circuit stops the supply of a pumping light power. Moreover, while the down detecting signal is generated, the supply of the lightwave signal by the electrical to lightwave signal converter is ceased. As mentioned in the above, since the amplification of the light power signal is restarted after the energy of carriers sufficiently decreased by spontaneous emissions of carriers, the light wave surge is not generated.

Abstract: In a method of monitoring an optical amplifier in an optical communication system, an optical signal is optically amplified in response to a drive current by an optical amplifier which includes at least one optically active element and a group of optically passive elements including a rare earth element doped optical fiber. The intensity of light emitted from the optically active element is monitored to generate a first monitor signal indicative of the intensity of light emitted from the optically active element. Also, the optical fiber is monitored for an optical amplification of the optical amplifier. The drive current is supplied to the optical amplifier based on the second monitor signal. The states of the optically active element and the group of optically passive elements are determined based on the first monitor signal and a second monitor signal corresponding to the drive current.

Abstract: A control circuit for reducing the output of an optical amplifier when reflected light associated with the output of the amplifier temporarily increases. An erbium-added optical fiber amplifies an input optical signal. Two optical detectors respectively detect the amplified optical signal and the reflected light. When a reflected light monitor signal does not exceed the level of a threshold signal, an output control circuit controls the intensity of an exciting light source in accordance with the an output light monitor signal. However, when the former exceeds the latter, the output control circuit reduces the output power of the optical signal. At this instant, the threshold level is lowered. As soon as the reflected light monitor signal becomes lower than the lowered threshold, an inverting amplifier causes the monitor signal to be restored to the original level.