Modulation Bandwidth Enhancement of Monolithically Integrated Mutually Coupled Distributed Feedback Laser

Modulation bandwidth enhancement of directly modulated semiconductor lasers (DMLs) has attracted broad interest to accommodate the tremendously growing demand for network traffic. In this paper, a monolithically integrated mutually coupled (IMC) laser for the O-band is demonstrated both numerically and experimentally. The direct modulation bandwidth was enhanced utilizing a photon–photon resonance (PPR) effect based on the mutual injection-locking technique. The IMC laser consisted of two distributed feedback (DFB) laser sections with a semiconductor optical amplifier (SOA) section in between. The relationship between the PPR frequency and SOA length was analyzed numerically to achieve a flat modulation response by optimizing the SOA length. Then, an enhanced 3-dB bandwidth of 38.7 GHz was realized experimentally, a nearly threefold enhancement over the modulation bandwidth of a solitary DFB laser at the same bias. Moreover, clear open eyes up to 40 Gb/s transmission over a 25-km single-mode fiber were achieved. Although the dynamic extinction ratio of the eye diagram was 1.1 dB, it can be further improved by increasing the mutual injection locking range of the IMC laser.

Radio Over Fiber-Based Wavelength Division Multiplexed/Time Division Multiplexed Passive Optical Network Architecture Employing Mutual Injection Locked Fabry-Perot Laser Diodes

We demonstrate a radio-over-fiber-based hybrid wavelength-division-multiplexed/time division multiplexed passive optical network (PON) to transmit 5 Gbps data rate to serve 32 subscribers. A broadband light source (BLS) is realized by mutual injection locking between two Fabry-Perot laser diodes at the transmission section to seed wavelength-division-multiplexed channels. Mutual injection locking technique is used to enhance the performance over single Fabry-Perot laser diode and 15 dB/Hz improvements in relative intensity noise(RIN) is realized in our proposed network system. All-optical up-conversion of a 10-GHz 1.25 Gbps on off keying radio frequency (RF) signal is achieved using one single-arm Mach-Zehnder modulator (MZM). Transmission performance over 25-km single mode fiber is investigated. Low bit error rate with enhanced eye-diagram is obtained in our proposed system. As a result, the radio over fiber (ROF)-based wavelength-division-multiplexed/time division multiplexed PON set up employing mutually injection locked Fabry-Perot laser diodes can be a better choice in high speed long-haul optical communication system.

Linewidth Narrowing of Mutually Injection Locked Semiconductor Lasers with Short and Long Delay

A simple and effective approach to semiconductor laser linewidth narrowing via mutual injection locking is proposed and demonstrated in both short and long delay regimes. A theoretical analysis is presented to investigate the linewidth behavior of semiconductor lasers under mutual injection locking. Experimental demonstrations in short and long delay regimes are implemented by integrated devices and a fiber link system, respectively. Locking condition and dependence of laser linewidth on coupling parameters in both regimes are studied, confirming mutual injection locking as a practical method for linewidth narrowing. For the short-delayed integrated lasers, a linewidth narrowing factor of 13 is demonstrated and sub-MHz linewidth is achieved, while for the long-delayed lasers coupled by fiber link, the intrinsic linewidth is reduced to sub-100 Hz.