First field trial using novel two-stage remotely-pumped EDF/distributed Raman hybrid inline amplifiers with 1.28-Tbit/s (32x43 Gbit/s) capacity over 528-km (6x88 km) DSF in the L-band

摘要

Enhancing SNR is a crucial issue for high-capacity long haul transmission across inline amplifier systems. Some enabling techniques such as new modulation formats and distributed Raman amplification (DRA) have been intensively studied [1, 2]. Some studies have focused on remote pumping since the technique, which uses remotely-pumped erbium-doped fiber (RP-EDF), can improve the optical SNR (OSNR) and so achieve ultra-long distance transmission, mainly in unrepeatered undersea systems [3, 4, 6-8] except for [5]. An inline-repeater transmission-experiment was reported in [5], in which 20 Gbit/s (8x2.5 Gbit/s) was achieved in the ～7-nm flat gain-band of a C-band EDF. All RP-EDFs reported to date have been C-band RP-EDFs. However, C-band RP-EDFs have insufficient gain flatness from 1530 to 1560 nm [3-8]. Gain reduction in the band results in a degradation in OSNR. Moreover, several field trials with ≥40-Gbit/s channel-rates and >1-Tbit /s WDM aggregate capacity have demonstrated system feasibility [9-11]. The record distance for straight-line trials reported to date is 351 km (4 x 87.8 km) of SMF with 64x43 Gbit/s capacity [11]. However, no field trial using RP-EDFs has been reported. This paper reports the first field trial using a novel RP-EDF together with DRA as an inline-type amplifier; 1.28-Tbit/s (40x43 Gbit/s) capacity has been achieved with 100-GHz spacing in the L-band over a record 528-km (6x88 km) of terrestrial installed-DSF in the straight-line configuration. The RP-EDF is the first L-band RP-EDF, which has a two-stage and double-pass type configuration. The RP-EDF yielded a high pumping efficiency and an excellent gain flatness from 1570 to 1600 nm. Moreover, both the RP-EDF and the DRA showed flat gain-spectra from 1570-1600 nm when they were pumped at 1470+1490 nm. Therefore, we can maximize OSNR improvement by using the combination of the RP-EDF and the DRA, namely "hybrid RP-EDF/distributed Raman amplifier".