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Two-section Fabry–Perot laser diodes can produce tunable radio frequency (rf)/microwave intensity oscillations (subcarrier) on the optical carrier without any active rf/microwave components. The frequency of the subcarrier is limited to a few Gigahertz for the free-running two-section Fabry–Perot laser diodes. A method for enhancing the frequency of the optically-generated subcarriers by using external optical injection is analyzed and demonstrated experimentally. It is shown that external optical injection can increase the effective tuning range by 70%, in the meantime reducing the power in the high-order harmonics.

The optical current-controlled oscillator (CCO) is an all-optical device capable of producing frequency-tunable intensity oscillations (subcarriers) on an optical carrier without any active radio frequency/microwave components. From a dynamic point of view, the CCO is a nonlinear optical system supporting the Hopf bifurcation and operating in the periodic orbit regime. This article presents the theoretical foundation for the optical CCO and its applications in optical communications involving subcarriers. Using one embodiment of the optical CCO employing a two-section Fabry-Perot laser diode, we present the static and modulation characteristics of the periodic-orbit subcarrier of the optical CCO. The performance of CCO-based all-optical subcarrier optical communication system is estimated using representative device parameters. The relationship between the capacity of CCO-based communication networks and the frequency-tuning range of the CCO is also established.

The dynamics of self-pulsating laser diodes with optoelectronic feedback have been experimentally studied. The frequency of the intensity oscillations exhibit staircase-like dependence on the bias current at low feedback levels and bistable dependence at high feedback levels.

The amplitude and phase noise of individual harmonic of self-pulsations in a two-section laser diode have been characterised experimentally. Both amplitude and phase noise are 1/f in nature for < 1kHz frequency offsets and white for > 10kHz frequency offsets.

Lutfur Rahman and Guifang Li, “Remote Synchronized Chaos in Laterally Coupled Semiconductor Laser Arrays,” Optics Communications, 138, 91-94 (1997).

We show that a solitarily-stable remote semiconductor laser can be driven into a chaotic state synchronized with the chaotic dynamics of a local master laser. The master laser, which is also solitarily stable, acquires its own chaotic dynamics when laterally coupled with other semiconductor lasers. Synchronization between the chaotic states of two remotely located lasers is robust for a wide range of parameter values. Transients towards synchronization take place within a time of the order of 10 ns.

Guifang Li, R. K. Boncek, Xiaolu Wang and D. H. Sackett, "Transient and feedback-sustained pulsation of laser diodes at 1300 nm," IEEE Photon. Technol. Lett., 7(8), 854-846 (1995).

We report the observation of self-sustained pulsation and transient self-pulsation in laser diodes at 1300 nm and the effects of optoelectronic feedback on the pulsations. Transient self-pulsation has a lifetime of a few minutes with frequencies up to 7 GHz. The linewidth of self-pulsation is on the order of 0.5 GHz. With optoelectronic feedback, the transient self-pulsation can be sustained and the linewidth significantly reduced to about 20 kHz. The center frequency of feedback-sustained pulsation is dependent on the passband of the bandpass filter in the feedback loop. The feedback sustained pulsation can be frequency modulated for applications in subcarrier multiplexed optical networks such as cable TV distribution and antenna remoting.

A method of subcarrier lightwave modulation based on the self-sustained pulsation (SSP) of laser diodes is presented. The tunable microwave/millimeter-wave frequency subcarrier is generated by the laser diode itself under proper DC biases. The subcarrier is frequency-modulated when the DC bias is superimposed with a small AC signal. No external modulation is needed. A theoretical analysis based on a double-section laser diode reveals that Hopf bifurcation is the origin of SSP. Theoretical calculations also show that the modulator has the potential of generating subcarriers up to 100 GHz by proper control of the device parameters V-channeled substrate inner-stripe (VSIS) GaAlAs laser diodes were used to generate 1-7-GHz SSP subcarriers. A preliminary subcarrier multiplexing (SCM) experiment demonstrated the transmission of 1-GHz modulation and video signals on a readily FM-modulated 6.3-GHz SSP subcarrier.