1.5- $\mu{\rm m}$ 10-Gb/s VCSEL Link for Optical Access Applications

We experimentally demonstrate the power budget improvement of a 10-Gb/s vertical-cavity surface-emitting laser (VCSEL) link by utilizing continuous-phase frequency-shift keying (CPFSK)/amplitude-shift keying (ASK) modulation format. We first measure the frequency modulation (FM) response of the VCSEL from 10 kHz to 10 GHz and then exploit dc-balanced line coding to utilize the flat region of the FM response. The CPFSK/ASK signals are generated by directly modulating the VCSEL and utilizing a delay interferometer (DI) for FSK-to-ASK conversion. We successfully transmit the signals over a 50-km dispersion-uncompensated link by optimizing the free-spectral range of the DI. Using the proposed scheme, we achieve > 5-dB improvement in the power budget compared with a conventional VCSEL link.