Transmission Networks  P AR T I Gbps/80 Gbps switch routers for the outer core network. We believe this network will enable us to meet the increasing demand for  broadband access and broadband multimedia services.  As of December 31, 2011, our transmission networks consisted of approximately 1.32 million fiber kilometers of fiber optic  cable for trunking and approximately 4.19 million fiber kilometers of fiber optic cable for local loop.  Synchronous digital hierarchy, or SDH, architecture is an advanced technology that allows for instantaneous rerouting  and eliminates downtime in the event of a fiber cut. In addition, SDH offers better reliability and performance for optical fiber  transmissions at a lower operating cost. In December 2002, we installed synchronous transport module 64 or STM 64, multiplexer  and 32-wavelength dense wavelength division multiplexing, or DWDM, equipment on our long-haul backbone network. Our STM  64 multiplexer can multiplex several low speed signals into a 10 gigabits per second, or Gbps, high-speed signal. DWDM equipment  uses a technology that puts data from different sources together on an optical fiber with each signal carried on its own separate  wavelength. Both STM 64 multiplexer and DWDM equipment can increase our network capacity. Furthermore, between 2003 and  2007, we deployed 32-wavelength optical add-drop multiplexer rings in Taipei, Taichung, Tainan and Kaohsiung. Between 2007  and 2011, we deployed 40/80-wavelength Re-configurable Optical Add-Drop Multiplexer, or ROADM, for backbone transmission  network in order to provide new data services such as gigabit Ethernet, fiber channel, 2.5 gigabit and 10 gigabit packet over SDH  and 10 gigabit Ethernet. We have already completed the deployment of 397 wavelength ROADM by the end of 2011. To meet the  demand for broadband services, we will install an optical cross-connect, or OXC, network and a next generation synchronous digital  hierarchy, or NG SDH, network, which provides gigabit Ethernet over SDH service, between 2009 and 2013. We have already  completed the deployment of 3,514 GbE OXC/NG SDH by the end of 2011. Based on the transmission network described above, we have been providing connection circuit service of 10 gigabit packet  over SDH and 10 gigabit Ethernet to the government’s Taiwan Advanced Research and Education Network since November 2006 and  continued the service until November 2012.  As part of our strategic focus on the internet and data markets, our local loop connections use ADSL technology. This  enables us to deliver high-speed internet, multimedia and other data services to our customers. Substantially all of our installed  telephone lines are capable of delivering ADSL services. As of December 31, 2011, we had approximately 4.21 million lines of  ADSL and had 2.1 million ADSL customers. In addition, the Ethernet-based FTTx system is also introduced into our access network  to provide broadband services, such as MOD, high speed internet access and VPN. As of December 31, 2011, we have constructed  approximately 4.05 million FTTx ports and had 2.4 million FTTx customers. Our FTTx service can offer high-speed broadband  internet access rates up to 1Gbps.  Domestic telecommunications network.  Our domestic public switched telephone network consists of 19 message areas  connected by a long distance network. As of December 31, 2011, we had 38 long distance exchanges, which are interconnection  points between our telecommunications network.  As of December 31, 2011, our NGN core network consisted of 798,100 local telephone subscribers, comprising of 448,000  Session Initiation Protocol-based, or SIP-based, and 350,100 Access Gateway-based, or AG-based, subscribers. In 2011, we initiated  a new extension of 349,000 AG-based subscribers. AG-based subscribers will be provided with the original services. SIP-based  subscribers access the NGN core network through broadband circuits and will have access to innovative value-added services in the  future along with the original services.  Our NGN Managed IP backbone network consists of an inner core network and an outer core network. We completed the  construction of our high-speed NGN Managed IP backbone network at the end of 2011 with 12 sets of 1.6 Tbps/640 Gbps switch  routers for the inner core network and more than 24 sets of 640 Gbps switch routers for the outer core network. The bandwidth of the  network is approximately 715 Gbps as of the end of 2011. We believe this network will enable us to meet the increasing demand for  Switching Networks  43