Research Of OTDR Based On USB Technology

With the growing development optical fiber technology, the application fields of optical fiber are more and more widely. From military to civil use, the optical fiber has closely linked for People’s Daily life and work. Optical fiber communication technologies use the optical fiber low loss, bandwidth, robust of high voltage etc merit, and become the mainstream of the modern communication field. The development of the optical fiber communication at the same time promoted the development of optical fiber testing technology. OTDR is a kind of optical fiber test instrument. It has gained wide application in optical fiber communication and optical fiber monitoring. And along with the rapid development computer technology and electronic technology, the performance requirements of OTDR ever more diverse, at present, the USB is a very extensive bus interface, compared with other interface, it has a hot swap, plug and play, fast speed, easy to use, cheap etc other advantages, and became a main way in the testing device.This paper researched a kind of OTDR of based on the USB and PC, put the computer technology and the optical fiber testing technology combined, make full use the information processing power of computer. The USB interface can realize communications between FPGA and host.This article chooses the USB control chip which is ISP1362series of Philips, this chip has the biggest characteristic is to accord with The OTG standard. USB OTG is a complement for USB2.0agreement, it has the double function characteristics, that is as a USB host function and USB device function, can realize the dynamic role conversion.FPGA is as the core of data acquisition system. In QuartusII environment, use VerilogHDL language to achieve sampling clock control and the USB control process. The software of super-computer use c#3.0of Visual Studio2008, it is a kind of brand-new object-oriented programming language, and the main job is to complete control interface, USB devices to identify, USB device for reading and writing programming.Finally, the OTDR data which is from the USB interface input proceed to analysis. Using wavelet packet technology to get the signal de-noising, and using the wavelet modulus maximum to position for mutation incident of OTDR curve; At the same time introduce approximate entropy characterized quantitatively the chaos of the signal, according to evaluation the wavelet denoising degree. The results show that, using the wavelet packet technology can effectively eliminate noise and maintain the original nature of mutation.