Abstract
The phase modulation (PM) and amplitude modulation (AM) of optical signals can be achieved using a direct-modulated (DM) optical injection-locked (OIL) semiconductor laser. We propose and theoretically analyze a simple method to extract the phase component of a PM signal produced by a DM-OIL semiconductor laser. The pure AM component of the combined PM–AM signal can be isolated by square-law detection in a photodetector and can then be used to compensate for the PM–AM signal based on an optical homodyne method. Using the AM compensation technique, we successfully developed a simple and cost-effective phase extraction method applicable to the PM–AM optical signal of a DM-OIL semiconductor laser.
Highlights
We recently reported the theoretical analysis of the phase modulation (PM) of an optical injection-locked (OIL) laser based on the direct modulation (DM) of a slave laser, the results of which demonstrated the successful enhancement of the PM range up to 360 deg using a cascaded connection of injection-locked laser stages.[15]
We found that a DM-OIL semiconductor laser exhibits a PM–amplitude modulation (AM) combined effect based on the coupled-rate laser equations
The typical homodyne detection method provides a PM–AM combined product that limits the application of DM-OIL semiconductor lasers
Summary
The generation and processing of high-speed optical signals are critical issues in current and next-generation information technology applications that require ultrahigh data rates, such as high-capacity communications inside data centers, optical interconnects, and supercomputers.[1,2] Among various optical signal generation and processing techniques, the phase modulation (PM) of optical carriers has been widely investigated because of its promise to satisfy the everincreasing requirements for high-speed data transmission.[3,4,5,6] The PM of an optical carrier is typically achieved using an external optical modulator, such as an acoustooptic or electrooptic modulator.[7,8] these external modulators exhibit several limitations, including large-form factors and high cost, and are typically difficult to integrate with other photonic devices.[9,10,11]. The proposed pure PM extraction technique enables the use of DM-OILs in real-field PM applications, such as complex-format optical signal generation, optical signal processing, coherent optical communications, and light detection and ranging (LIDAR) systems
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