| 摘要 |
PROBLEM TO BE SOLVED: To easily provide a variable wavelength light source by providing a variable wavelength light source, a multipath Mach-Zehnder interferometer for receiving a signal from the light source and supplying main output and one or more secondary outputs, and a feed back circuit for adjusting the variable wavelength light source. SOLUTION: A light source 9 having a stable wavelength includes at least one variable wavelength light source 10, a multipath Mach-Zehnder interferometer(MMZI) 11, a plurality of photodetectors 12A, 12B for monitoring the output of the interferometer 11, and a feed back circuit 13 for adjusting the operation wavelength of the variable wavelength light source 10. The multipath Mach-Zehnder interferometer 11 includes a pair of multi-mode couplers and a plurality of wave guides having different optical paths between the couplers. The variable wavelength light source 10 is preferably constituted by tunable lasers 10A to 10D. A typical feed back circuit 13 uses two photodiodes 12A, 12B as the front ends of the different trans-impedance amplifiers 21A, 21B. |
