A lumped Raman amplifier for all-Raman long-haul and ultra-long haul optical communications systems based on highly
non-linear Photonic Crystal Fiber (HNL-PCF) is proposed and demonstrated. Applications for such an amplifier are
discussed, focusing on discrete loss compensation for L-Band all-Raman reconfigurable systems. The main
specifications required for this and similar applications have been analyzed, and include Power Conversion Efficiency
above 30%, Net gain of about 15dB, and output power in the range of 20-23 dBm. Additional specifications such as
Noise Figure, Multi-Path Interference (MPI), and transient suppression are also considered. In order to achieve the
required specifications, the HNL-PCF should exhibit high Raman efficiency and low attenuation at pump wavelengths of
1470-1500nm, resulting in a Figure of Merit (FOM) above 8 dB<sup>-1</sup>W<sup>-1</sup>. The splice loss of the HNL-PCF to conventional
Single Mode Fiber is also shown to be critical, and should not exceed 0.5 dB. Initial samples of HNL-PCF have been
characterized, and it has been demonstrated that high Raman efficiency and low splice loss are achievable, while further
work is being carried out to increase the FOM. Finally, an experimental demonstration of 10Gb/s WDM transmission
using a prototype Lumped Raman Fiber Amplifier based on HNL-PCF is presented.investigated and compared to similar VCSELs with etched mesa.
We have developed an array of ten uncoupled, single-mode ridge-waveguide lasers for spectral beam combining at 980 nm, which are based on an aluminium-free active region. Single emitters deliver 0.4 W CW at 0.7 A with an M<sup>2</sup> beam quality factor of 1.6. The array has an output power of 2.1 W CW at 3.15 A. The maximum wall-plug efficiency is 48%. Spectral beam combining is achieved through a low-quality-factor external cavity. We extract more than 1.5 W from the cavity with a good beam quality. The ten peak wavelengths range between 968 and 982 nm. The source was validated by pumping an EDFA with similar results as a single wavelength source.