Designing transmit optical amplifiers for the current roll out of optical communication constellations

Abstract

There are a number of parametric challenges in designing transmit optical amplifiers for the current deployment of optical communication constellations. Constellations are often aligned to channel wavelengths defined by the Space Development Agency (SDA) Tranche 1 Optical Communications Terminal Standard, which requires duplex operation at 1536.61 and 1553.33nm. We present an experimental characterisation supported by numerical modelling, of duplex operation up to 10W at both channel wavelengths and discuss performance limits. The characterisation includes power, out-of-channel amplified spontaneous emission (ASE) content and in-channel ASE content / noise figure determined from time-domain extinction measurements. For an output power of 10W, stimulated Brillouin scattering (SBS) can readily limit the delivery of optical power over relatively short fiber lengths. We also present the growth of a Stokes wave as a function of output power, delivery fiber length and fiber type experimentally. These results showing good agreement with theory, and set design limits on peak power transmission. These peak power considerations being of particular interest for pulse position modulation (PPM) encoding which are required in both the SDA and Consultative Committee for Space Data Systems (CCSDS) 142.0-B-1 standards. The CCSDS and SDA standards both require a sinusoid amplitude modulated tracking tone. We present the limits of the design space of achievable modulation depth, as function of amplifier design, modulation condition and operating wavelength & power. A good agreement between experimental and numerical results is found.