Philippe Bousselet

Second-order distortion improvements or degradations brought by erbium-doped fiber amplifiers in analog links using directly modulated lasers

Within lightwave analog amplitude-modulated (AM) CATV systems using directly modulated lasers, erbium-doped fiber amplifiers (EDFAs) act upon the signal distortion because of the interaction between the laser chirp and the EDFA wavelength-dependent gain. This interaction is theoretically investigated in order to predict the EDFA-induced distortion. The relevant gain tilt characteristic for analog applications and the way to measure it are described. Expected and measured distortions at the EDFA output are in excellent agreement. Fiber amplifiers are found to decrease the signal distortion level when the gain tilt is negative, i.e., for wavelength above the gain maximum.<<ETX>>

320-Gb/s (32 x 10 Gb/s WDM) transmission over 500 km of conventional single-mode fiber with 125-km amplifier spacing

Thirty-two 10-Gb/s channels spaced by 100 GHz are transmitted over 500 km of dispersive fiber (D>+19 ps/nm/spl middot/km) with 125-km amplifier spacing. This is made possible by the use of 3 in-line dual-stage flat-gain erbium-doped fiber amplifiers (EDFAs) incorporating dispersion-compensating fiber. The transmission performance is significantly improved when a 9-km section of dispersion compensating fiber is added at the receiver end, for the longer-wavelength half of the multiplex.

1480-nm pumped erbium-doped fiber amplifiers with optimized noise performance for AM-VSB distribution systems

Within analog video transmission systems, optical amplifiers have to display simultaneously good noise and output power performance because of the very stringent carrier-to-noise ratio requirements imposed by the AM-VSB modulation format. We show, theoretically and experimentally, that properly designed forward 1480-nm pumped erbium-doped fiber amplifiers can deliver +16 dBm saturated output power with noise parameter (n/sub sp//C/sub x/) as low as 3.5dB. These amplifiers do not exhibit significant degradation of their noise performance when the input powers are as large as +3 dBm. These characteristics make 1480-nm pumped amplifiers suitable for AM-VSB transmission systems.<<ETX>>

Effect of band location on characteristics of distributed Raman amplification

The impact of attenuation spectrum and effective area of link fiber has been experimentally and numerically assessed regarding the required pump power and effective noise figure for the S-band compared to C-band and XL-bands. Compared to the C-band and XL-band, it is shown that 15% more pump power is required in the S-band compared to the C-band while 1 dB more is observed for the effective noise figure compared to the C-band. The XL-band offers better a noise figure (2 dB lower than in the S-band) with similar power performance. Indeed, the increase of effective area and decrease of material Raman coefficient with wavelength reduces the benefit brought by a lower attenuation coefficient. However, attenuation at the pump wavelength is paramount for the determination of the best noise figure. Installed fiber characteristics, particularly concerning possible bending loss in the XL-band, will finally determine the best suited solution.

EDFAs with improved gain-flatness owing to a new pump design

A new pump source based on a semiconductor array coupled with an external cavity laser is shown. Its broad output spectrum allows to improve the EDFA gain flatness while reducing manufacturing cost.

High-brightness spectrally combined array of 980-nm single-mode emitters

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 M2 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.

Spectral Beam Combining of a 980-nm Laser Array for EDFA Pumping

A 980 nm laser source based on spectral beam combining is proposed for the pumping of EDFAs. A 1.5 W power is extracted from the laser cavity. Improvement of the EDFA gain flatness is demonstrated.

BER validation of ring-doping cladding pumped EDFAs for dense WDM applications

By means of back to back BER analysis, we have compared 2 amplifiers (using ring doping and conventional core doping) having similar performance in terms of gain, output power and noise figure. Amplification of the signal out of the fiber core like in the ring-doping technique does not impair the BER measurement nor add penalty to the analysis. We can conclude that this type of fiber can be used in amplifiers for the future high-bit rate WDM systems.

dBm output power from an engineered cladding-pumped Yb-free EDFA for L-band WDM applications

We have demonstrated a saturated output power of +26 dBm with a cladding-pumped Yb-free erbium-doped fiber amplifier owing to the matching of the multimode pumps wavelength with the erbium absorption spectrum. These results corresponded to saturated output powers of +23 dBm with a single multimode module and +26 dBm with two sources used in combination. Moreover, in the flat-gain regime, an output power of +24 dBm has been obtained for only 1.76 W launched pump power. Since the amplifier incorporated only packaged devices, this will make its gain flatness characteristics and high output powers available soon for the next generations of high bit-rate WDM systems.