910 nm Single-Mode VCSELs and its Application for Few-Mode Transmission over Graded-Index Single-Mode Fibers

Abstract

Short distance optical communication in data centers has been dominated until now by multimode-fiber links based on multimode vertical cavity surface emitting lasers (VCSELs). Their large wall-plug and energy efficiency, as well as the relaxed requirements for fiber connectivity, reduces the overall cost of the system. A single-mode (SM) VCSEL has lower NA and smaller spot size making it suitable for coupling the light into the standard single-mode fiber. We show that a SM VCSEL can be implemented at 910 nm with high bandwidth (> 25 GHz) and high side mode suppression ratio (> 40 dB) at wavelengths beyond 850 nm to add more capacity for SM VCSEL transmission. The performance of the 910 nm SM VCSEL is evaluated at 25 Gbit/s using two single mode graded index fibers. These fibers are single mode at 1310 nm and 1550 nm, enabling their use for long-reach and high bandwidth applications, while still providing enough bandwidth for short wavelength, short-reach, and cost sensitive applications. Error free $(\text{BER} data transmission of 25 Gbit/s across 1 km is achieved using a 910 nm optimized fiber and 150 m transmission using a fiber optimized for dual wavelength (850 nm and 910 nm) transmission.