Abstract: An optical amplifier apparatus is provided with an optical amplifier and a 4-port optical circulator. The optical amplifier optically amplifies first signal light entered from an input port thereof, and then outputs the first amplified signal light from an output port thereof. The optical circulator contains first to fourth ports, and sequentially outputs light that is inputted from each of these first to fourth ports to the next port thereof. The input port of the optical amplifier is connected to the second port, and the output port thereof is connected to the third port. An optical transmission apparatus having a break point detecting function is provided with an optical time domain reflectometer for outputting an optical pulse along the same direction as that of the first signal light in addition to the optical amplifier apparatus and an optical transmitter module.

Abstract: In an optical amplifying apparatus, a detour optical line is employed in addition to such an optical amplifier for amplifying light having a first wavelength of “&lgr;1” and for outputting the amplified light. This detour optical line is operated in such a detour manner that the light having the first wavelength of “&lgr;1” is selectively entered into the optical amplifier, and also the light having the second wavelength of “&lgr;2” is not selectively entered into the optical amplifier. The light having the first wavelength of “&lgr;1” which constitutes the original signal light may be optically amplified by the light amplifier, and thereafter the amplified signal light is outputted to a rear-sided optical fiber.

Abstract: A signal light monitor having a first optical branching coupler disposed in an optical fiber transmission line for branching a part of an inputted signal light and outputting a first branched light, a first wavelength tunable filter for transmitting a first particular wavelength component included in the first branched light and outputting a transmitted light and a first sweeper for sweeping a transmission center wavelength of the first wavelength tunable filter within a range of the first particular wavelength component. The transmitted light outputted from the wavelength tunable filter is received by a first optical receiver and converted into an electric signal and sampled by a first sampling device. The first sampling data is stored in a first storage device. A waveform of electric signal from optical receiver is stored in the first storage device as a series of data.

Abstract: An optical amplifier for amplifying and outputting an input light signal, comprises an optical light amplifier unit (10), a tunable wavelength filter (30), a signal light detection unit, and a control circuit (100). The optical amplifier unit (10) amplifies the input light signal and outputs an amplified light signal. The tunable wavelength filter (30), into which the amplified light signal is inputted and which transmission light wavelength is swept, outputs a filter output signal. The signal light detection unit detects a signal light level of an amplified output component in the amplified light signal in response to said input light signal. The control circuit (100) controls a gain of said optical amplifier unit based on the signal light level. Further, the signal light detection unit of the optical amplifier according to the present invention comprises a peak detection unit (60) and a background light detection unit (70). The peak detection unit (60) detects a peak light level of the filter output signal.

Abstract: A line monitor comprising: an optical signal input section for permitting an optical signal to be input; optical signal output means for outputting an optical signal; a fiber grating including a section with a periodically varied refractive index, the optical signal, which has entered the section with a periodically varied refractive index, in its component with a predetermined specific wavelength being reflected while the remaining component of the optical signal is output from the optical signal output means; first optical signal withdrawal means for allowing the optical signal in its component with a specific wavelength to withdraw into the outside of the fiber grating; and photoelectric conversion means for converting the optical signal in its component with a specific wavelength taken out from the first optical signal withdrawal means to an electric signal.

Abstract: An optical amplifier circuit includes an optical amplifying unit for amplifying a light signal having a predetermined wavelength to output an amplified light signal, first and second optical branching units each for branching a part of the amplified light signal to output branched light signals, and a band rejection optical filter for removing light within a center wavelength band to allow only spontaneous emission light to be selectively transmitted. A subtractor outputs a control signal according to a difference between the light signal branched by the first optical branching unit and the spontaneous emission light. A controller controls the output of the amplified light signal based on the control signal, thereby to maintain precisely a constant light output level.