Ando Electric Company

Nippon Telegraph and Telephone Corporation

Zhixien Li

Haruyoshi Uchiyama

Toshio Kurashima

Yasushi Sato

Kazuo Aida

Shoji Adachi

Kaoru Shimizu

Yasushi Satoh

An object of the present invention is to provide an optical fiber strain measuring apparatus which can perform precise measurement without causing any fluctuation in signal level. To achieve the above object the present invention comprises: a polarization plane rotation device 105 which rotates a plane of polarization of an optical pulse; a photo-directional coupler 106 which projects an optical pulse projected from the polarization plane rotation device 105 into an optical fiber 107 to be measured, and projects out backscattering light produced in the optical fiber 107 to be measured; a polarization plane rotation device 160 which rotates a plane of polarization of a reference light; a light mixing device 109 for mixing the backscattering light projected out from the photo-directional coupler 106 and the reference light projected from the polarization plane rotation device 160; and a signal processing section 111 which detects the mixed light projected from the light mixing device 109, converts the detected light into an electrical signal and subjects the electrical signal to a predetermined operational processing to obtain a measurement waveform.

Optical fiber strain measuring apparatus

An optical pulse signal produced by modulating a continuous laser light by means of a first pulse having a period sufficiently shorter than the atomic lifetime in the upper energy state of a rare earth doped fiber is input to an optical amplifier to be measured, while an output signal from the optical amplifier is modulated by a second pulse synchronized with the first pulse and having a phase difference relative to the first pulse which can be optionally set so that rapid phase adjustment relative to the first pulse is possible based on the phase at the time of minimum optical power. The noise figure of the optical amplifier is then measured based on, the maximum photoelectric power (P.sub.AMP +P.sub.ASE) and the minimum photoelectric power P.sub.ASE of the resultant optical signal.

Method and apparatus for measuring the noise figure of an optical

Coherent light emitted from a coherent light source 1 is sent as a probe beam through a connector 31 into an optical fiber being measured. A portion of this beam is sent to an optical frequency converter 100 to form an optical pulse train having a frequency which is frequency-swept in steps of a designated frequency at a designated periodicity, and an optical pulse having a designated frequency is extracted from the optical pulse train by an electro-optic switch 18 and sent to the optical fiber being measured. Then, a signal beam exiting the optical fiber being measured is heterodyne-received by means of a local beam passing through either a connecting optical fiber 6 side or a frequency shifter 7 side according to the selection of optical switches 4 and 5. Consequently, it is possible to measure the characteristics of the optical fiber by means of a BOTDR, BOTDA or a COTDR.

Optical fiber characteristic measuring device

Growing community of inventors

Tokyo, Japan

Zhixien Li