| 摘要 |
PURPOSE:To enable merely using an etalon plate as a Fabry-Perot resonator, to reduce in size the whole system and to stably set a frequency interval by employing a method of sweeping the frequency of a reference laser as means for sweeping a frequency axis for searching the oscillation frequency of a plurality of lasers. CONSTITUTION:After the second output light 12 of an optical branch unit 7 transmits a quartz glass etalon plate 13 in which both-side reflectivities, area degree and parallelism are so set as to become fineness 30 with 1.5 of refractive index and 2mm of thickness, it is incident on a second photodetector 14. A pulse like light is incident on the photodetector 14 when the oscillation frequencies of 1.55mum band wavelength variable distribution Bragg's reflection type semiconductor lasers 1, 2 coincident with the resonance frequency of the plate 13, the number of pulses generated during one sweeping period is determined by the ratio of the variable frequency width of 250GHz in one sweeping period to the free spectrum range of 75GHz of the etalon plate, there are three in the respective lasers. An electric signal from the detector 14 is applied to the first input terminal 16 of a controller 15. After emitted lights from the 1.55mum band distributed feedback type lasers 17-21 are transmitted through optical isolators 22-26, they are applied to the second input terminal 31 of the controller 15 through second optical composite units 27, 28, 30. |
