R.G.S. Plumb

Dynamic analysis of radiation and side-mode suppression in a second-order DFB laser using time-domain large-signal traveling wave model

In this paper, we have developed a relatively simple algorithm to calculate the large-signal dynamic response of DFB lasers by solving the time-dependent coupled wave equations directly in the time domain. The spontaneous emission noise, longitudinal variations of carrier (hole burning) and photon densities as well as that of the refractive index are taken into consideration. To demonstrate the power of this straightforward algorithm, the model shows how the side-mode suppression ratio in devices with high /spl kappa/L and a /spl lambda4: phase shift is significantly affected by the radiation in the second-order DFB laser. The time-dependent radiation pattern in grating-coupled surface-emitting lasers is also calculated for the first time. >

Large-signal dynamic behavior of distributed-feedback lasers including lateral effects

The large-signal behavior of DFB lasers is analyzed, including lateral as well as longitudinal variations in carrier density, photon density, and refractive index. The effective index method and other approximations are used to reduce the complex three-dimensional problem to one dimension. The coupled wave and carrier rate equations are then solved in a self-consistent manner. Lateral spatial carrier hole burning and lateral diffusion are found to affect the relaxation oscillation frequency and damping rate of DFB lasers, depending on their detailed structure. The effective time-averaged linewidth enhancement factor is also affected. In symmetric AR-coated /spl lambda//4 phase-shifted lasers the side mode suppression ratio can be deteriorated significantly by lateral spatial hole burning when kL is large. >

Gigabit pulse position bistability in semiconductor lasers

The paper briefly reviews the major forms of optical bistability in active optical devices compatible for use in gigabit optical communication systems, and reports an entirely new optical bistability for the first time. Unlike previous devices, the two bistable states of the optical device are each a series of picosecond optical pulses at 1 GHz or greater repetition rates, and are distinguished by a half period temporal shift between their temporal positions in relation to a clock pulse. The bistable device is based on a gain switched semiconductor laser. Theoretical studies suggest 100-ps switching speeds might be achieved, and experimental results are reported indicating optically triggered switching times of 500 ps.

Directly-modulated DS-DBR tunable laser for uncooled C-band WDM system

A tunable DS-DBR laser is demonstrated for uncooled WDM C-band channel generation with tight spacing (50 GHz) and low thermal drift (plusmn 2.5 GHz) up to 70degC. 2.5 Gb/s direct modulation with transmission over a 75 km link is achieved

Modal bistability in twin-ridge injection lasers

This paper reports on the first observations of a promising new form of optically triggered modal bistability in semiconductor lasers. The bistable mechanism involves a switch between the degenerate in-phase and antiphase coupled modes of an index-guided, twin-ridge laser operating at 1.3 μm wavelength. Experimental results have indicated sub-picojoule bistable switching with switching times of less than 250 ps. Possible limitations of device performance are discussed, with particular reference to asymmetry of the ridge structure.

Indoor hybrid infrared-radio access network

A novel hybrid infrared-radio access network for indoor nano-cells is introduced, in which radio is used as a back-up if the infrared propagation path is inoperable due to incomplete coverage or shadowing. The proposed system is originated from the radio over fiber concept, associated with arrayed waveguide gratings (AWG) and subcarrier multiplexing (SCM) technologies, and capable of serving multiple users simultaneously with multi-services. A model is designed for the proposed hybrid infrared-radio access network, using the VPI software package to investigate the physical layer issues, with emphasis on modulation schemes. Physical characteristics of infrared channels using intensity modulation with direct detection (IM/DD) are presented. The performance of a hybrid infrared-radio AWG-SCM access network with 4 subcarrier frequencies, 2.4, 5, 17 and 24 GHz, using different modulation schemes is discussed in detail.