<title>End-to-end performance in the downstream and upstream direction over a hybrid fiber-coax broadband access system</title>

Abstract

The design of the optical link for the downstream (from a head-end or a central office to a fiber node near the customer premises) and upstream (from the customer premises to the head-end or central office) transmissions in a hybrid fiber-coax access system is reviewed in detail. Particularly, the end-to-end bit-error performance of 64-QAM transmission using a hybrid fiber-coax system test bed designed for delivery of 77 AM-VSB and 25 64-QAM video channels covering the frequency band 54 - 702 MHz was studied. Error-free QAM transmission was achieved with the use of modulated analog carriers and Reed-Solomon (204,188) error-correction coding indicating that in hybrid fiber-coax systems transport of AM- VSB and 64-QAM signals can be realized maintaining both analog and digital performance requirements. Results are also presented on the design and choice of optical transmitters for the upstream path. The role of laser clipping in setting system signal-to-noise and dynamic range for error-free QPSK transmission in the upstream direction is described.