J.-C. Bouteiller

Pump-pump four-wave mixing in distributed Raman amplified systems

This paper describes the four-wave mixing (FWM) interaction of several Raman pumps and its effect on optical-signal-to-noise ratio and Raman gain. In this paper, the modeling of the combined Raman and FWM effects is explained and is used for the impairment investigation. We compare the relative importance of amplifier parameters. In particular, the paper shows how wide pumps increase the regions of forbidden zero-dispersion wavelength and increase the penalty regions in the signal band. Fiber parameters beyond zero-dispersion wavelength (dispersion slope, effective area, and Rayleigh scattering) are also investigated but show little impact. Finally, the paper considers nonuniform spans and shows that the use of short cables makes pump-pump FWM a likely problem.

WDM transmission over multiple long spans with bidirectional Raman pumping

We investigate the feasibility of WDM transmission over multiple spans that are twice as long as those typically used in commercial systems. Using longer spans reduces the number of repeater sites, potentially lowering the operating costs of medium- and long-haul terrestrial systems. We show that bidirectional Raman pumping is a key enabling technology. In particular, we demonstrate the benefits of high levels of codirectional Raman gain, up to 10-dB more than is used in transmission experiments with standard span lengths. Then, we transmitted 40 /spl times/ 10.66 Gb/s with uncorrected bit-error ratios better than 10/sup -9/ using 200-km spans of nonzero dispersion fiber with 14.5-dB of Raman co-gain over a reach of 2400 km. We also measured the maximum amount of span loss that was tolerable for a given system reach for 200-km span transmission at 10 Gb/s. After optimization at twelve distances (800 to 3000 km), we found that the tolerable span loss increased by 1 dB for each 200-km reduction in reach.

High co-directional Raman gain for 200-km spans, enabling 40 /spl times/ 10.66 Gb/s transmission over 2400 km

Using 200-km spans with 14.5-dB Raman co-gain, we transmitted 400 Gb/s error-free over 2400-km of True Wave/sup /spl reg// REACH fiber. With bidirectional Raman pumping, span lengths could be doubled, reducing operating expenses for medium-to long-haul systems.

Dual-order Raman pump providing improved noise figure and large gain bandwidth

This paper reports a single Raman pump laser capable of covering the bandwidth of three regular pump lasers with a 1.5 dB improved noise figure and a 0.9 dB improvement in system performance, in a distributed Raman amplifier.

A high-efficiency power-stable three-wavelength configurable Raman fiber laser

:A highly efficient configurable three-wavelength cascaded Raman laser suitable for broadband Raman amplification is demonstrated. The power at each wavelength is adjusted by varying the reflectivity of fiber grating output couplers. Measurements of the power stability at each wavelength show that the source is stable.

Stretched ultrashort pulses for high repetition rate swept-wavelength Raman pumping

We demonstrate a novel, high repetition rate, swept-wavelength Raman pump source. The pump is based on stretched femtosecond pulses, initially generated in a passively modelocked, erbium-doped, fiber laser, and wavelength shifted in highly nonlinear, dispersion shifted fiber. The pump wavelength has a linear sweep in time, with a repetition rate of 69 MHz. The pump has a center wavelength of 1470 nm, a full-width at half-maximum (FWHM) of 31 nm, and an average power of 350 mW. We characterize the pump by performing pump propagation experiments and electrical spectrum measurements of signal lasers amplified with the swept-wavelength pump.

Configurability of a three-wavelength Raman fiber laser for gain ripple minimization and power partitioning

The performance of a 3/spl lambda/RFL with variable OC reflectivities was investigated in 60 km, 100 km and 140 km transmission spans. The data indicates that this device is practical and can provide stable broadband optical amplification. A gain ripple minimum of 1.1 dB in a 100 km span, in agreement with simulations, is achieved with an OC voltage precision of 25 mV. The gain ripple /spl Delta/G and power partition deviation /spl Delta//spl rho/ voltage sensitivities were found to be /spl sim/0.01 dB/mV and /spl sim/0.04%/mV, respectively. This low sensitivity means control of the output powers of a multi wavelength RFL is not considerably more complicated than controlling multiplexed individual lasers.

Experimental investigation of the impact of NZDF zero-dispersion wavelength on broadband transmission in Raman-enhanced systems

Two nonzero dispersion fibers with different zero-dispersion wavelengths (ZDW) were evaluated for C+L-band, Raman-enhanced systems. With an optimized ZDW, 80/spl times/42.7 Gb/s transmission over 800-km can be achieved without forward-error-correction or per-channel post dispersion optimization.

Raman fiber lasers as pumps for Raman amplification

This article describes Raman fiber lasers and their application as pumps to a Raman amplified optical communication system. Single wavelength, multiwavelength and dual-order devices are described. The advantages of Raman fiber lasers compared to semiconductor diodes are also discussed.

Supercontinuum generation in a highly nonlinear fiber using a continuous wave pump

Supercontinuum generation with a bandwidth greater than 247 nm is demonstrated in a highly nonlinear fiber by pumping with a continuous wave Raman fiber laser in the anomalous dispersion regime. The continuum showed good long-term power stability.