Introduction to the application of RF optical transmission RF over Fiber
In recent decades, microwave communication and optical telecommunications technology have developed rapidly. Both technologies have made great progress in their respective fields, and also led to the rapid development of mobile communication and data transmission services, bringing great convenience to people’s lives. The two technologies of microwave communication and photoelectric communication have their own advantages, but they also have some disadvantages that cannot be overcome. Photoelectric transmission requires physical networking, and there are some shortcomings in the flexibility, fast networking and mobility of construction. Microwave communication has some shortcomings in long-distance transmission and large capacity, and microwave needs frequent relay amplification and re-transmission, and the transmission bandwidth is limited by the carrier frequency. This led to the integration of microwave and optical Fiber transmission technology, that is, Radio over Fiber(ROF) technology, which is often referred to as RF over Fiber, or radio frequency remote technology. The most widely used field of RF over Fiber technology is the field of optical fiber communication, including mobile base stations, distributed systems, wireless broadband, cable TV, private network communications and so on. In recent years, with the rise of microwave photonics, RF over Fiber technology has been widely used in microwave photon radar, UAV communication, astronomy research and other fields. According to the different types of laser modulation, laser communication can be divided into internal modulation and external modulation, the commonly used is external modulation, and the RF over Fiber based on external laser modulation is described in this paper. RF over Fiber links are mainly composed of optical transceiver, transmission, and ROF links, as shown in the following figure:
A brief introduction to the light part. LD is commonly used DFB lasers (distributed feedback type), which are used for low noise, high dynamic range applications, and FP(Fabry-Perot type) lasers are used for less demanding applications. The most commonly used wavelengths are 1064nm and 1550nm. The PD is a photodetector, and at the other end of the fiber optic link, the light is detected by the PIN photodiode of the receiver, which converts the light into an electrical signal and then into the familiar electrical processing step. The optical fiber used for intermediate connection is commonly single-mode and multi-mode optical fiber. Single-mode fiber is commonly used in the backbone network because of its low dispersion and low loss. Multimode fiber has a certain application in local area network because it is cheap to manufacture and can accommodate multiple transmissions at the same time. The attenuation of the optical signal in the fiber is very small, only ~0.25dB/km at 1550nm.
Based on the characteristics of linear transmission and optical transmission, ROF links have the following technical advantages:
• Very low loss, fiber attenuation less than 0.4 dB/km
• Fiber ultra-bandwidth transmission, fiber loss independent of frequency
• Link with higher signal carrying capacity/bandwidth up to 110GHz• Electromagnetic Interference (EMI) resistance (inclement weather does not affect signal)
• Lower cost per meter • Fiber is more flexible and lightweight, weighing about 1/25 of the waveguide and 1/10 of the coaxial cable
• Easy and flexible arrangement of electro-optic modulators (for medical and mechanical imaging systems)
Post time: Mar-11-2025