Patent ID: 8442406

Claim:
A coherent receiver, comprising: a receiver front end for converting a received partial response optical signal into a partial response digital signal; a pre-filter for converting the partial response digital signal into a full response digital signal; an equalizing device for equalizing the pre-filtered full response digital signal; a phase recovering device for performing a phase recovery of a signal equalized by the equalizing device; and a post-filter for post-filtering a signal having undergone a phase recovery by the phase recovering device, so as to recover the full response digital signal to the partial response digital signal, wherein a transfer function of the post-filter is same as that of the partial response digital signal, wherein the pre-filter uses the following transfer function H Pre-Filter (z) with respect to a partial response signal having a transfer function H PR (z)=A(1+z −1 ) m (1−z −1 ) n : H Pre - Filter ⁡ ( z ) = 1 A ⁡ ( 1 + α ⁢ ⁢ z - 1 ) m ⁢ ( 1 - α ⁢ ⁢ z - 1 ) n , in which A is other item, m and n are integers larger than or equal to 0 but not being 0 at the same time, 0<α<1.