| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an optical transmission apparatus capable of making a desired extinction ratio compatible with long-distance fiber transmission. <P>SOLUTION: A semiconductor laser 13 outputs a modulated optical signal obtained by directly modulating frequency of a carrier wave according to a baseband electric signal 11. An optical filter 14 is composed of an asymmetric Mach-Zehnder interferometer and converts a frequency modulation component of the modulated optical signal into an amplitude modulation signal. An FSR of the asymmetric Mach-Zehnder interferometer meets an illustrated formula wherein an extinction ratio of a transmission optical signal 15 is denoted by ER, output of the transmission optical signal 15 normalized with a strength of the modulated optical signal 17 is denoted by P, a spectrum half-value width of the modulated optical signal 17 is denoted by W, a suppression ratio of a residual sideband included in the transmission optical signal 15 is denoted by S, optical frequency detuning of a space optical signal of the modulated optical signal 17 is denoted by f<SB>0</SB>, and optical frequency detuning of a spectrum center frequency of the modulated optical signal 17 is denoted by f<SB>c</SB>. <P>COPYRIGHT: (C)2010,JPO&INPIT |
