New generation of ultrafast transmitters for 5G optical data transport

M. Osinski, G. A. Smolyakov, N. J. Withers, S. A. Nazib, T. A. Hutchins-Delgado, and H. S. Lee
University of New Mexico, New Mexico, United States

Keywords: whistle-geometry ring laser; cascaded ring lasers; injection locking; high-speed modulation

The continuing increase of transmission rates and capacity at all levels of telecommunication and wireless networks raises demand for very high-speed, low-cost optical transmitters. We present our concept for low-cost, small-size injection-locked directly modulated laser sources with very high modulation bandwidths exceeding 100 GHz that could revolutionize the future of optical data transport in 5G networks and optical telecommunication in general. Optical injection locking has been actively researched for its potential to improve ultrahigh frequency performance of semiconductor lasers for both digital and analog applications. We have proposed a new injection-locking scheme, based on unidirectional whistle-geometry ring lasers (WRLs) monolithically integrated with distributed Bragg reflector laser masters. Numerical analysis of the modulation response of a single injection-locked WRL shows a very significant reduction in the modulation efficiency between low frequency and the resonance frequency (low-frequency roll-off), which severely limits the achievable 3-dB modulation bandwidth. By combining advantages of strong injection locking (to dramatically enhance the resonance frequency) and cascaded arrangement of WRLs (to eliminate the low-frequency roll-off in modulation response), a new class of high-performance ultrafast, easy-to-use functional chips is expected to emerge.