I. Introduction
100 Gigabit Ethernet was standardized by IEEE802.3ba in June 2010, and 4 × 25 Gb/s LWDM (Local area network Wavelength Division Multiplexing) method (100GBASE-LR4) was adopted as a standard for 10km single mode fiber transmission [1]. 100 Gigabit Ethernet optical signal is composed of four lanes with the rate of 25.78125 Gb/s, and the center wavelengths for each lane are assigned to 1295.56 nm (lane 0), 1300.05 nm (lane 1), 1304.58 nm (lane 2), 1309.14 nm (lane 3).