Final Report Chapter 4 Trend on Communication Technology CHAPTER 4 TREND ON COMMUNICATION TECHNOLOGY 4.1 Basic Transmission Technology Due to the prevalence of the internet and the growing number of users and use applications, the majority of services are extra high volume imaging services requiring broadband. Compared with the coaxial cables system and the radio communication system in the past media, advanced fiber optic cable system has become main stream due to the spread of broadband and a large increase in speed. Optical transmission of 1.55μm has become possible by broadband (several 10s THz) at a low transmission loss (0.2 dB/km) by using fiber optic cables in conjunction with semiconductor laser technology. Wavelength Division Multiplex technology, originally developed to cut down on the enormous time and expense required for laying optical fiber submarine cable has become universal as a fast transmission method that can handle extra large volumes. By paraphrasing the equipment at both ends, the fiber optic cable can utilized effectively with the Wavelength Division Multiplex (WDM) communication system, avoiding additional costs for the fiber optic cables. It will be able to handle a great increase in network traffic caused by the prevalence of broadband. Following a growing trend of FTTH application, it can be used by separating uplink and down link signals, connecting superimposed composite signals of telecommunication and broadcasting networks to a single core. There are two kinds of technical solutions as follows:  CWDM (Coarse WDM) Multiplexing optical signals up to 16 wavelength with 20 nm separation from 1410nm to 1610 nm (Multiplexing equipment up to 8 wavelength is commonly used)  DWDM (Dense WDM) Since it can combine more than tens of wavelengths, it is used by telecommunication providers as a backbone. Long distance transmission is made possible by the availability of special optical amplifier and dispersion compensator. Reusable optical Add-Drop Multiplexers, (ROADM: Re-configurable Optical Add/Drop Multiplexer）have recently become available. Configuration of DWDM system is given in Figure 4.1-1 and Figure 4.1-2. Single Core Optical Fiber λ1 ・ ・ λn DWDM Multiplexer/De-mu ltiplexer DWDM Multiplexer/De-mu ltiplexer RAODM Drop λ1 ・ ・ λn Add Source: prepared by Survey Team Figure 4.1-1 Configuration of the DWDM System 4-1