Amplification of high-bandwidth phase-modulated optical signals from integrated-optics phase modulators at 793 nm is experimentally demonstrated using an injection-locking technique. Off-the-shelf wide-bandwidth integrated-optics modulators are power limited at 793 nm owing to photorefractive damage of the LiNbO<sub>3</sub> waveguides. Typical optical input powers for these devices at this wavelength are less than 10 mW with optical output powers typically less than 1 mW. To amplify the outputs of these modulators, we injected the phase-modulated light into an antireflection-coated 100-mW single-mode diode laser. With the injection-locking technique, small-signal gains of 23 dB are demonstrated with good signal fidelity up to bandwidths of 3 GHz. A bandwidth limitation is found at approximately 3 GHz for sinusoidal phase-modulated signals, above which signal fidelity is seriously degraded. This limitation is significantly less than the measured relaxation oscillations of ∼5.6 GHz, suggesting a new limitation to injection locking of phase-modulated signals. Amplification of binary-phase-shift-keyed-modulated signals to 6 Gbit/s is also demonstrated with no bit errors over the 256-bit test sequences.
© 2002 Optical Society of America
(060.5060) Fiber optics and optical communications : Phase modulation
(130.3120) Integrated optics : Integrated optics devices
(140.3520) Lasers and laser optics : Lasers, injection-locked
(300.6240) Spectroscopy : Spectroscopy, coherent transient
Randy R. Reibel, Zeb Barber, Mingzhen Tian, W. Randall Babbitt, Zachary Cole, and Kristian D. Merkel, "Amplification of high-bandwidth phase-modulated signals at 793 nm," J. Opt. Soc. Am. B 19, 2315-2321 (2002)