Abstract: A telemetry optical fiber has a first end optically coupled to a signal source/detection module. A conversion module is optically coupled to a second end of the telemetry optical fiber. The conversion module includes an interferometer having a pair of optical paths with an optical waveguide arranged to be included in each one of the optical paths. The interferometer is arranged to produce an interference pattern to indicate the phase relationship of optical signals input to the pair of optical paths from the signal source/detection module. A phase modulator is arranged to phase modulate optical signals guided by the optical waveguide. A sensor head that produces a voltage proportional to a quantity being measured is connected to the phase modulating apparatus and arranged to provide a modulating signal to the phase modulating apparatus such that the interference pattern indicates the magnitude of the measured quantity.

Abstract: An analog optical transmission apparatus includes a semiconductor laser module, a bandpass filter, a distortion level detection circuit, a control signal generation circuit, and a distortion erasure circuit. The semiconductor laser module includes a semiconductor laser for converting a multi-carrier analog signal into an optical signal and outputting the optical signal and a light-receiving element for receiving the optical signal from the semiconductor laser and converting the optical signal into an electrical signal. The bandpass filter extracts only a specific distortion component from the electrical signal output from the light-receiving element. The distortion level detection circuit detects a level of the distortion component output from the bandpass filter. The control signal generation circuit generates a control signal corresponding to the distortion component level output from the distortion level detection circuit.

Abstract: In an output port switching device in an N-WDM system, plural ports are switched by a change-over switch 18, and a backup light source path 19 linked to the change-over switch 18 has a wavelength-variable light source 23. A first multiplexer 14 wavelength-multiplexes plural optical signals output from the plural ports, and a trouble-occurring port monitoring mechanism portion 17 monitors occurrence of a trouble on the basis of an optical signal split from the output optical signal. The change-over switch 18 selects and switches an optical signal to which the trouble is detected, and the backup light source path 19 is controlled so that the wavelength thereof is substantially coincident with the wavelength of the optical signal to which the trouble is detected, and the optical signal thus controlled and the output optical signals of the first multiplexer are multiplexed by a second multiplexer 15.