WDM Transmission over Dispersion Shifted Fiber in L-Band with 25 dB Span Loss

摘要

Erbium-doped fiber amplifiers (EDFAs) operating in the L-band wavelength range of 1570 to 1610 nm have enabled WDM transmission over dispersion shifted fiber (DSF). WDM transmission was previously problematic over DSF in the C-band (1535 to 1565 nm) due to four-wave mixing (FWM). Although there have been numerous experimental demonstrations of WDM transmission over DSF in L-band, most of these have used either relatively low powers [1, 2, 3], non-standard data formats (duobinary) [4], lower bit rates (below 10 Gb/s) [5] or large (200 GHz), or unequal channel spacings [6]. While these experiments demonstrate the feasibility of L-band systems, there has been no demonstration of a 10 Gb/s WDM transmission system with 100 GHz channel spacing operating in L-band over dispersion shifted fiber with the power margins that would be required to ensure reliable transmission in a deployed system. Low-error rates can easily be obtained at powers of only -2 to 0 dBm per channel with typical fiber span losses of 18-22 dB, however, higher powers must be used in deployed systems to ensure that a low error-rate is maintained in the event of increased span loss (eg. 25 dB) from degradation in the system. However, system powers cannot be increased indefinitely because of fiber nonlinearities. Even with its larger dispersion in L-band, transmission over DSF is still susceptible to fiber nonlinear effects such as FWM and cross-phase modulation (CPM) at moderate powers since its core size is about 50 μm~(2) compared with that of 80 μm~(2) for conventional single mode fiber. Both launched power and dispersion map must be carefully chosen for transmission at powers above 0 dBm per channel.