Advances in optical power budgets and bandwidth capacity of broadband networks.

摘要

In this dissertation, we demonstrate record optical power budgets and novel architectures for broadband networks that provide ten times more bandwidth per subscriber than any system commercially available today. The compensation, and in some cases exploitation, of fiber nonlinearities is a key element in obtaining the record results. Using high-power optical amplifiers, low-noise optical preamplifiers and the beneficial effects of optical pulse compression, a 67.5 dB optical power budget for a 2.5 Gb/s system is obtained without the use of any intermediate repeaters or amplifiers.;Optical pulse compression is achieved through an interaction between anomalous fiber dispersion and a linear frequency chirp generated by self-phase-modulation (SPM) nonlinearity in the optical fiber. By solving the fiber propagation equation, the SPM-induce pulse compression is theoretically found. The optical pulse compression measured from eye diagrams is in very good agreements with the calculated values.;Several applications that exploit the large power budgets for broadband applications are demonstrated: a digital video transport experiment in which a 2.5 Gb/s signal is broadcast to more than 8,000 subscribers located up to 50 km away; a four-channel (10 Gb/s) wavelength-division-multiplexed signal is broadcast to 40 subscribers located 200 km away; and a commercial 186 km fiber-optic system is built that is the largest unrepeatered SONET OC-48 span in the United States.;We perform comprehensive modeling of dense wavelength-division-multiplexing (DWDM) networks that transport multi-level digital signals such as M-QAM requiring signal-to-noise ratios of 35 dB or more. System impairments due to chirp-induced distortions, laser clipping and stimulated Raman scattering (SRS) fiber nonlinearity (which places a fundamental limit on the number of DWDM channels) are analyzed. The coupled partial differential equations describing SRS are solved and the maximum capacity of DWDM systems is determined to be 40 channels. A twenty-channel DWDM system using more than 650 km of optical fiber is tested that provides twice the number of DWDM channels and ten times more bandwidth per subscriber as commercial systems. Detailed tests are performed on both the analog video signals and 256-QAM digital signals transported over the network Measurements of fiber nonlinear effects such as SRS, four-wave-mixing, and cross-phase-modulation reveal that our modeling of linear and nonlinear fiber effects in broadband networks is accurate.;The technologies and architectures investigated here will prove to be the building blocks for advanced broadband networks that will provide high-speed, interactive broadband services to subscribers in the near future. Our research has furthered the goal of developing reliable broadband networks that are similar to passive optical networks and provide very large bandwidth to subscribers.