Abstract

Laser-diode-pumped erbium-doped fiber amplifiers (EDFA) have recently demonstrated all their potential for very long haul transmissions [1]. In-line EDFA application is clearly identified for long undersea links. However, repeaterless transmissions have many applications, especially over 250 km lengths. Compared to direct detection, heterodyne detection allows to achieve a very high receiver sensitivity, increasing the overall link budget [2], Optical amplifiers highly improve this budget, particularly by compensating for the insertion loss of the external phase modulator in DPSK systems. We report a 565 Mbit/s DPSK transmission experiment at 1.532 μm using an EDFA module at the emission, operating in gain saturation regime. Pumped by laser diodes, this optical post-amplifier delivers an amplified output power exceeding +13 dBm, leading to a repeaterless power budget of 62.9 dB. This gives the potentiality to design over 350 km repeaterless links by use of a pure silica core fiber.

© 1990 Optical Society of America