| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a compact and inexpensive light receiver capable of stably demodulating a signal light based on a differential quadrature phase shift keying (DQPSK) modulation. <P>SOLUTION: The light receiver generates a delay time difference corresponding to an amount of one symbol between polarization elements to which a DQPSK signal light is perpendicular by performing 45° linearly polarized light incidence of the input DQPSK signal light to a PANDA type fiber 12. The signal light is branched into two by a half mirror 15 and transmitted to first and second paths. A π/2 relative birefringent amount difference is given to a light propagating in each path by a 1/4 wave plate 17 provided in one of the paths. Each light propagating in the first and second paths is separated into two polarization elements which are perpendicular to each other at polarization separating sections 16A, 16B. Each polarization element is received at receivers 18, 19, respectively, and a common mode element and a perpendicular element of the DQPSK signal light are demodulated. <P>COPYRIGHT: (C)2006,JPO&NCIPI |
