Low-chirp isolator-free 65-GHz-bandwidth directly modulated lasers

Today, in the face of ever increasing communication traffic, minimizing power consumption in data communication systems has become a challenge. Direct modulation of lasers, a technique as old as lasers themselves, is known for its high energy efficiency and low cost. However, the modulation bandwidth of directly modulated lasers has fallen behind those of external modulators. In this Article, we report wide bandwidths of 65-75GHz for three directly modulated laser design implementations, by exploiting three bandwidth enhancement effects: detuned loading, photon-photon resonance and in-cavity frequency modulation-amplitude modulation conversion. Substantial reduction of chirp as well as isolator-free operation under a reflection of up to 40% are also realized. A fast data transmission of 294.7Gbps over 15km of a standard single-mode fibre in the O-band is demonstrated. This was achieved without an optical fibre amplifier due to a high laser output power of 13.6dBm.