INTRODUCTIONOptical fiber technology is finding wide ranging applications in many areas including communications and sensors. In applications, such as "Fiber to the Home" (FTTH), large quantities of fiber optic components will be used and subjected to environments not usually encountered in "Central Office" applications. In Figure 1 a typical "POTS /Video" subscriber loop topology is shown. Telephone Cent r a I node service (POTS) will operate in a bidirectional mode over a single fiber at one wavelength and video will be broadcast over a second wavelength to the subscriber. From the figure it can be seen that the link for a single subscriber requires two 3 dB couplers at wavelength 1 and two Wavelength division multiplexers operating at wavelengths 1 and 2. If interactive video, such as Video -Phone, is required an additional two 3 dB Tx couplers, operating at wavelength 2, will be needed. A 1 Rx Modu leDevices at the subscriber end of the system will be located in a box on the wall of the residence /office or located in a pedestal on the curb -side. In both scenarios the devices will be subjected to the full range of environmental parameters, from the extremes of -40 C in winter to high humidity at +40C in the summer. Inside the Remote Electronic Site (RES) temperatures of up to 80 C could be experienced at certain locations. Tx )12 Module Figure 1. Subscriber loop network for "POTS" and video.Consequently, it is important from the maintenance cost perspective that installed fiber optic devices operate over these extremes of conditions and have mean time to failures in excess of 20 years. In addition to meeting these specifications there is a requirement to manufacture these devices in high volume at low cost. In order to meet these last two requirements it is necessary to fully comprehend the manufacturing process with respect to process limits -performance specifications -reliability trade -offs.The application of modern manufacturing philosophy with statistical process control and careful product design argues that there is no reason for defects.In this paper details will be presented of the testing techniques that allow the process limits to be specified and the testing levels that enable tracking of the performance of the manufactured devices.
jNTRODUCTIONWith the telephone trunk lines in place, the telephone operating companies and CATV corporations are intending to bring fiber optic technology directly to the home using a singlemode bidirectional fiber network. The obvious advantages are the enhanced services that could be provided by the enormous information capacity available using optical fiber. Such services include: a. Video phone. b. Home banking and shopping. c. Automated utilities recording. d. Home security systems. e. CATV. f. High definition TV (HDTV).Many systems configurations have been put forward and several trials are presently underway. The most typical configuration is shown in Figure 1 and uses a single fiber to the home in a bidirectional format. This system can provide POTS ( Plain Old Telephone Service) and with a WDM overlay, could provide video and other services. Remote Electronics Site DistributionThe "last mile' Singlemode bidirectionalCoupler or WVDM Xmit Receive Module Figure 1. Schematic of single fiber -to-the -home system, In order for a fiber -to -the -home system to be economically competitive with respect to coaxial and twisted -pair approaches, low -cost active and passive components such as transmitters, receivers, couplers, connectors and WDMs are required. In this paper, we show that the wavelength dependence of passive fiber optic couplers strongly affects system performance and ultimately system cost. The utilization of Wideband couplers with their minimal wavelength dependence1-4 will be addressed in terms of improved system performance and reduced system cost through the relaxation of laser wavelength tolerances. As system innovations such as the utilization of Wideband couplers improve the economics of the fiber-to -thehome services, we shall see considerable market penetration by the technology over the next 2 to 3 years.
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