3. Conclusion

Since research began in the 1970s, semiconductor optical amplifiers have continued to advance in terms of both technology and performance, as their applications have diversified. Although they have been supplanted by erbium-doped fiber optic amplifiers for linear amplification in very long-distance links, their functionalities go far beyond pure amplification, thanks to the exploitation of their non-linear properties to realize all-optical signal processing functions. These functions were extensively studied in the 1990s. However, the need to use complex modulation formats to increase the spectral efficiency of optical links, thanks to constant advances in electronic signal processing, led to a disaffection with these all-optical signal processing techniques in the 2000s. Despite this, SOAs are of particular interest for applications in the fast-developing fiber-optic local area networks...