Broadband flat-noise Raman amplifier using low-noise bidirectionally pumping sources

Abstract

We propose and e.rperimental!v demonstrate an optimised bi-directional pumping scheme that realizes a less than 0.7 dB.flatness over C-and L-bands of both Raman gain and optical noisefigure. simultaneous!v. In order to usr,/onrard-primpiny. .for the proposed method. a new rype of pump laser having low relative intensip noise is also developed -I S z 17 --

Research on bidirectionally pumped Raman amplifiers: noise and transmission performance

“…As a result, bi-directional pumping can adopted in broadband WDM systems to equalize the tilted noise spectra, which has been realized experimentally by Kado et.al [7,8]. A novel optimization method is given in [11] to equalize the OSNR profile of ultra-wide band systems by using bi-directionally pumping without changing the original gain profile, and an optimized result is shown in fig.2.…”

“…However, bi-directionally pumping scheme can equalize OSNR tilt by adding proper forward pump diodes to a backward pumped RA [6]. According to Fludger's conclusion [7], the crosstalk from a forward pump to a signal channel can be ignored if the pump RIN is less than -110dB/Hz. So bi-directionally pumping can be a practical and reliable method to improve system performance by using 'quiet' forward pump diodes [8].…”

Optimal design of flat-gain and flat-noise wide-band fiber Raman amplifiers

“…Designing higher capacity and longer distance WDM transmission systems requires both gain and noise spectra over a wide signal band to be flat [2]. But both stimulated Raman scattering and wavelength dependence of fiber loss degrade the signal power and the OSNR especially in shorter wavelength band of Fiber Raman Amplifier [3].…”

“…In order to compensate these degradations, we can optimise the signal evolution in the span in the following methods:Firstly, since optical amplification prior to transmission loss can generally suppress the subsequent amplified spontaneous emission (ASE) noise, forward pumped Raman amplifier can have better noise performance than backward pumped one, therefore, combining backward and forward Raman pumping will get better OSNR [2]- [3].The Second one is the use of effective-area management, such as dispersion-managed fibre in the span to distribute the Raman gain more evenly along the fibre [4]- [7].The third method is the demonstration of feasibility of second-and higher order Raman pumping in a distributed amplifier, which is another way reaching the same goal [8]- [9].…”

RIN Mitigation and Transmission Performance Enhancement With Forward Broadband Pump

“…Unlike other pump lasers, the RIN of the output signal using this broadband laser does not increase dramatically when the pump power increases, and therefore signal power profiles can be adjusted for different nonlinearity compensation techniques [7,11,12]. In addition, compared with BW-pumping only, FW broadband pumping reduces the noise figure (NF) tilt across the amplification band and leads to a flatter gain spectrum [13].…”