Investigation of coherent spectral and incoherent wavelength/time optical code division multiple access (O-CDMA) systems

Continued Internet growth is prompting the deployment of optical fiber-based local access networks throughout the world to meet increasing bandwidth demands. To enable flexible bandwidth allocation and the possibility of enhanced security within these networks, this work investigates optical code division multiple access (O-CDMA), an access technique that enables multiple users to broadcast across a shared fiber through optically encoded transmission. The work focuses on two different encoding methods, spectral phase encoded time spreading (SPECTS) and time/wavelength coding.; The SPECTS technique encodes signal pulses through phase manipulation of the spectrum. The limitations caused by coherent beat noise and multiple access interference is analyzed, and techniques to mitigate their effects are experimentally demonstrated. Synchronous transmission, Walsh codes, and optical thresholding and time gating are all effectively employed on a SPECTS testbed, enabling it to support 32 users at 10 Gb/s/user with 20% spectral efficiency. Testbed simulations reveal the possibility of supporting up to 100 users, and a field trial utilizing integrated, silica-based encoders/decoders shows the viability of the SPECTS technique in a realistic telecommunications environment.; In time/wavelength coding O-CDMA, signals are represented as a unique sequence of multi-wavelength pulses, defined by a code. This work develops a particular time/wavelength code set designed to optimize spectral efficiency, derived from Golomb rulers. Analysis and simulation of the codes establish design parameters for an O-CDMA technology demonstrator, and the implementation is able to support 16 users operating at 1.25 Gb/s/user at 10% spectral efficiency. A comparison of the two O-CDMA techniques reveals that time/wavelength codes have better performance than SPECTS in a coherent beat noise-limited regime, but cannot provide asynchronous transmission between users. If the absence of coherent beat noise, SPECTS outperforms time/wavelength codes.; For completeness, this work also investigates optical label switching, which enables higher data throughput in wider area networks. The work focuses on the double sideband subcarrier technique and analyzes its performance, as limited by dispersion- and nonlinearity-induced RF fading. A field trial demonstrating key optical router functions validates the technique.