Abstract

A number of VSB-AM system experiments have been conducted in the past two years^1,2. All of these experiments utilize a directly modulated 1.5 μm DFB laser diode as the signal source. Linear lasers with higher power and lower relative intensity noise (RIN) are required to improve system dynamic range. This paper is the first report of a VSB-AM signal source based on a linearized 1.5 μm Mach-Zehnder (MZ) intensity modulator³ and a continuous wave Erbium doped glass laser. A high power Erbium amplifier serves as the post amplifier.⁴ VSB-AM system performance is degraded when laser phase noise is converted to amplitude noise by fiber dispersion and fiber reflections. The low phase noise of the Erbium glass laser provides high system immunity to laser phase noise conversion.⁵ The use of a balanced external modulator provides a chirpless intensity, modulated signal. This means that fiber with minimum dispersion at 1.3 μm can be used with the 1.5 μm source laser without degradation from second order distortion products.⁶

© 1991 Optical Society of America