Cascaded VCSEL-to-VCSEL all-optical injection for spectral defragmentation and switching using optical transmitter cross gain modulation

The exponential growth of data traffic in current optical communication networks require higher capacity for the bandwidth demands at a reduced cost per bit. All-optical signal processing is a promising technique to improve network resource utilization and resolve wavelength contention associated with flexible spectrum. This is achieved without necessarily employing optical to electrical signal conversions. In this paper, we experimentally present a novel, spectral efficient technique for defragmentation and wavelength switching on a cascade of vertical cavity surface emitting lasers (VCSELs). This is based on cross gain modulation of the optical transmitter. A 10 Gbps intensity modulated master VCSEL lasing at 1549 nm was used for optical power injection into the side modes of two slave VCSELs. The injection results in energy transfer between the lasing modes, causing data inversion on the transmission wavelength. The master lasing wavelength was tuned from 1546.5 to 1551.7 nm resulting in a 5.2 nm or 650 GHz spectral width by varying the bias current. A total of 9 continuous 50 GHz spaced WDM channels with nonoverlapping nominal frequencies and uniform guard bands were generated. This can be used to attain seamless defragmentation and bandwidth optimization for effective spectral resource management. The novel technique is flexible in terms of modulation formats and accommodates various formats with spectrally continuous channels, thereby fulfilling the future bandwidth demands with transmissions beyond 100 Gbps per channel while maintaining spectral efficiency.