VCSEL Based ROF Link Transceiver

With demand for substantial growth in optical communications, the Radio-Over-Fiber (ROF) technology is widely used. As the key component of ROF systems, vertical cavity surface emitting laser (VCSEL) can be direct modulated with high-speed. The highest modulation rate is over 20Gbps. Compared with common edge-emitting lasers, VCSEL has many advantages, such as lasing with low threshold current, dynamic single longitudinal mode, easy coupled with optical fiber, and high-density two-dimensional array, etc. The research of multi-wavelength, high modulation rate VCSEL earned more and more attentions.This article describes the development of ROF technology, the VCSEL structure characteristics and advantages as a high-speed modulated optical source, describes various kinds of optical modulation principles. This article designs a kind of VCSEL based ROF link Transceiver, with the wavelength of 850nm, and modulation rate greater than 2.5Gbps. This article describes the principles of all parts of modules of the transceiver circuits, analyzes the difficulties and design rules of microwave circuit. Transceiver described in this article could modulate and transmit microwave by VCSEL in a wide frequency range, it has got a good test results. The article also compares the scheme of direct modulation with the external modulation. Experiments show that the frequency range from 218MHz to 2.9GHz, the whole transfer function of Transceiver is greater than OdB. This article also tests the frequency range which needs to meet two conditions, output power greater than-lOdBm and fundamental power greater than 30dB above the second harmonic. Experiments show that the Transceiver achieves the transmission requirements of high bandwidth and high output power with the frequency range from 1.72GHz to 2.8GHz.