| 摘要 |
PURPOSE:To shorten the rise time and the fall time of a lamp voltage by constituting a biasing phase modulating part and a lamp phase modulating part by forming a pair of electrodes against an optical waveguide of a phase modulator, respectively. CONSTITUTION:As for a phase modulator 20, one end side optical waveguide 21 and the other side optical waveguide 25 are formed in parallel. With respect to the optical waveguide 21, a pair of electrodes 32, 33 and 42, 43 are formed, respectively and one end side biasing phase modulating part 31 {length l0-(la-alpha)} and one end side lamp phase modulating part 41 (length la-alpha) are constituted. With respect to the optical waveguide 25, a pair of electrodes 36, 37 and 46, 47 are formed, respectively and the other end side biasing phase modulating part 35 {length l0-(la+alpha) and the other end side lamp phase modulat ing part 45 (length la+alpha) are constituted. Also, setting length la>l0/2, a crest value of a lamp voltage can be made small without enlarging the dimensions of the modulator 20, and the performance of a speed meter is improved. |
