Lukasz Krzczanowicz

RIN-penalty mitigation and transmission performance improvement using forward propagated broadband first order Raman pump

We demonstrate that using a broadband pump enables forward-propagated first order distributed Raman amplification by mitigating RIN-associated penalty. This extends the reach of 10 × 120 Gb/s DP-QPSK WDM transmission up to 7499 km, compared with other commercially available pumps. Moreover, using this Raman scheme maintains uniform/symmetric signal power distribution and requires low pump power.

Noise performance improvement of broadband distributed raman amplifier using dual order bidirectional pumping

A low-noise broadband bidirectional Raman pumping scheme combining dual order co-pumps is proposed. The improved noise figure without RIN increase is compared experimentally and numerically with conventional pumping schemes for distributed amplification over 70 nm.

Performance characterization of high gain, high output power and low noise cascaded broadband discrete Raman amplifiers

In this paper, gain, noise and nonlinear performance characterization of cascaded broadband discrete Raman amplifiers with different gain fibre combinations is presented. We numerically demonstrate the design of a backward-pumped cascaded dual stage broadband (∼70 nm) discrete Raman amplifier with high gain (∼19 dB), low noise (∼ 6 dB noise figure) and lower nonlinear penalty by optimizing two different types of gain fibres.

Hybrid discrete Raman/EDFA design for broadband optical amplification in metro WDM systems

A novel design of a broadband discrete Raman/EDFA hybrid amplifier is proposed. A broadband signal of 84 channels across 75 nm is experimentally amplified and the gain contribution of each amplifier stage is shown. The amplifier consists of a discrete Raman amplifier using a DCF fibre pumped at three 14×× nm wavelengths, which is followed by a 1480 nm pumped erbium doped fibre. An average gain of 15.4 dB and gain flatness of ± 1.7 dB with no gain equalising elements is achieved.

High gain, flattened, discrete Raman fiber amplifier and its transmission performance

The capacity of Erbium-doped amplifiers (EDFA) systems is rapidly being approached, and thus research is increasing in alternative technologies which can deliver broader gain spectrum than EDFAs to increase system capacity [1]. Fiber Raman Amplifiers (FRAs) provide gain in any spectral region provided that a suitable pump and fiber are available. Distributed amplifiers using the transmission fibre as a gain medium are used to improve noise performance but discrete Raman amplifiers also have the capability of extending the optical telecommunication bandwidth. Broadband gain can be achieved if multiple pumps are employed, however, gain flatness needs appropriate design of multi-pump configuration. In this experiment as shown in 1a, nonlinearity was used to spectrally broaden a 1455nm first order pump by propagating through a short length of TrueWave fiber with zero dispersion wavelength near the pump wavelength [2]. A very low power of the broadened pump was then used as a seed for the 1365nm second order pump, to counter-pump the gain fiber in this way a flattened Raman gain profile over 40 nm bandwidth can be achieved. The Raman gain fiber used was, 4.5km Inverse Dispersion Fiber (IDF), with attenuation 0.23dB/km, dispersion −44 ps/nm/km at 1550nm, dispersion slope −0.128 ps/nm2/km, and effective core area 31 μm2. The remnant pump was filtered via a second WDM coupler and dumped via an angled connector. The total loss for the Raman amplifier was ∼ 4dB and on-off gain can be as high as 25dB depending on the pump powers.

Noise and transmission performance improvement of broadband distributed Raman amplifier using bidirectional Raman pumping with dual order Co-pumps

We demonstrate a low noise bidirectional broadband distributed Raman pumping scheme combining dual order co-propagated pumps without increasing the signal RIN level. The noise performance improvement is compared experimentally and numerically with conventional counter-pumping only and bidirectional pumping with only a 2nd order co-pump for a 70nm bandwidth and 61.5km distributed Raman amplifier. The proposed broadband pumping scheme shows 1.2dB maximum noise figure improvement and extends the long-haul transmission reach up to 6150km with a Q-factor improvement of ~0.7dB compared with counter-pumping only scheme.

Impact of front-FBG reflectivity in Raman fiber laser based amplification

We experimentally analyze the impact of front-FBG reflectivity in ultra-long Raman laser amplifiers performance, showing Q-factor penalties in excess of 1 dB for FBG reflectivities above 10% in a 30 GBaud DP-QPSK transmission system.