Performance analysis of a digital fiber optic link incorporating gain‐levered laser diode transmitter

Abstract

In this paper, digital modulation performance of two‐section, multiple quantum well gain‐levered laser diode in a fiber optic link is analyzed. This study involves numerical simulation of gain‐levered laser diode along with single‐mode fiber for evaluating gigabit rate digital transmission. The optical link performance is analyzed by evaluating the eye diagram, extinction ratio, and quality factor for different bit rates, modulation current, and fiber lengths. The results are compared with unlevered or normal laser diode–based fiber optic link with similar operating conditions. A 12‐dB improvement in extinction ratio is obtained for gain‐levered laser diode when the longer section and shorter section currents are kept as 30 and 0.5 mA, respectively. The Q parameter is found to increase with increasing modulation current in the gain‐levered case, and a maximum Q factor of 11 is obtained for a modulation current of 5 mA. The Q value is improved by a factor of 8 and 5 at 1‐ Gbps and 10‐Gbps data rates, respectively, under gain‐levered condition, when compared to normal laser diode–based link.

Numerical simulation and analysis of dual base transistor laser

“…Equation (9) gives rate of change of photon density in the quantum well, τ p is the photon life time in the active region and C is the spontaneous recombination coefficient. Solving the above coupled rate Equations ( 5)-( 9), provides the photon density, electron density present in the virtual state and quantum well in both longer and shorter sections of the active region.…”

“…Large optical gain in laser diodes finds numerous applications in digital optical logic circuits, high speed switching and for obtaining high modulation depth in direct modulation. [1][2][3][4][5][6][7][8][9][10] Gain switching provides higher optical power output for the given electrical input in active optical devices and is useful to overcome the coupling and transmission losses in the passive waveguides. Gain lever laser diodes have interesting property of providing maximum gain for a particular current compared to normal laser diode.…”

“…Gain lever laser diodes are investigated for radio over fiber applications and digital switching. [6][7][8][9][10][11][12] Gain lever effect in laser diodes is realized by splitting the active region into two isolated sections with ratio ranging from 0.1 to 0.9. Due to sub linear nature of the gain versus carrier density characteristics in quantum well active regions, a large change in the carrier density in one section of the laser (longer section) results due to a small change in injection current in the other section (shorter section).…”

“…Gain lever laser diodes have interesting property of providing maximum gain for a particular current compared to normal laser diode. Gain lever laser diodes are investigated for radio over fiber applications and digital switching 6–12 . Gain lever effect in laser diodes is realized by splitting the active region into two isolated sections with ratio ranging from 0.1 to 0.9.…”

“…Pocha et al 8 evaluated the electrical and optical gain lever effect in double quantum well InGaAs laser diode and reported an AM efficiency enhancement of 7 and 4 dB in electrical and optical gain respectively, compared to normal laser diode. Piramasubramanian et al 9 analyzed the modulation performance of gain levered laser diode in the fiber optic link. A 12 dB enhancement in extinction ratio (ER) is reported for gain levered laser diode compared with normal laser diode.…”