25-Gb/s OOK Transmission Using 1.5-<inline-formula> <tex-math notation="LaTeX">$\mu{\rm m}$</tex-math> </inline-formula> 10G-Class VCSEL for Optical Access Network

Abstract

We explore the possibility of transmitting 25-Gb/s on–off keying (OOK) signals generated by using a 1.5- μ m 10G-class vertical-cavity surface-emitting laser (VCSEL) over standard single-mode fiber (SSMF) for optical access applications. A transistor-outline-can packaged VCSEL having a 3-dB modulation bandwidth of 7 GHz is utilized to transmit the 25-Gb/s signals. We experimentally investigate the transmission performances of OOK signals obtained from two different transmitter schemes: with and without a delay interferometer (DI) at the output of the directly modulated VCSEL. In order to maximize the transmission distance without using bulky and lossy dispersion compensation modules, we optimize the extinction ratio of the signals and apply the electrical equalization at the receiver. Also optimized is the free-spectral range (FSR) of the DI when it is utilized. The experimental results show that we can successfully transmit the 25-Gb/s OOK signals over 33- and 45-km long SSMF with and without the DI, respectively. The use of DI not only alleviates the band limitation of the VCSEL but also significantly improves the receiver sensitivity of the 25-Gb/s OOK signal up to 30 km. Moreover, a larger power budget is achieved for transmission distances shorter than 25 km when a DI having an FSR of 25 GHz is utilized at the output of the VCSEL.