Francois Boubal

Network application and system demonstration of WDM systems with very large spans (error-free 32/spl times/10 Gbit/s 750 km transmission over 3 amplified spans of 250 km)

We present the network applications of WDM systems with very large spans. Enabling technologies are low loss fiber, large launch powers, Raman preamplification and forward error correction. An experiment using all these technologies is presented.

4.16 Tbit/s (104 /spl times/ 40 Gbit/s) unrepeatered transmission over 135 km in S+C+L bands with 104 nm total bandwidth

104 /spl times/ 40 Gbit/s unrepeatered transmission over 135.9 km is demonstrated on S+C+L bands (1492-1596 nm) using S-band lumped Raman amplifiers. The system implements distributed Raman pre-amplification over continuous bandwidth of 104 nm.

25 GHz spaced DWDM 160/spl times/10.66 Gbit/s (1.6 Tbit/s) unrepeatered transmission over 380 km

Unrepeatered transmission of 160 25 GHz spaced channels at 10 Gbit/s over 380 km is demonstrated. The combination of recent advanced technologies, such as DWDM multiplexing/demultiplexing, large pump power, remote amplification, in-line filtering and FEC, allow this record transmission to be achieved.

Raman amplification in unrepeatered submarine systems pushes the limits of distance and bandwidth

Raman amplification is a key technology for unrepeatered transmissions as it allows to widely increase both span length and optical bandwidth in a very simple manner. We review in this paper recent record demonstrations and installed systems where Raman amplification fulfills its role as a mean to reach very long repeaterless distances and to expand into new spectral areas.

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.

Tolerant low-loss three-lens coupling system for 1.48-μm unstable-cavity lasers

A 1.48-micrometer unstable-cavity laser is coupled into a single-mode fiber using three microlenses. Reproducible coupling of very high power is demonstrated with different types of lenses (plano-convex or bi-convex, with different apertures). Over 550 mW in single-mode fiber were reproducibly reached; to our knowledge, it is the highest power coupled into a single-mode fiber from a single semiconductor laser at this wavelength. Tolerance measurements on all of the coupling elements of a three-lens system are reported for the first time; an unexpected very large tolerance on the axial displacement of the second lens was measured. Results and interpretation with the aid of Gaussian and aberration simulations are also presented. Finally, we report on the first realization of a module with 46% chip to fiber coupling efficiency.