Optical Networks - _11_3 Fiber to the Curb (FTTC)_128

Optical Networks - _11_3 Fiber to the Curb (FTTC)_128 - 638...

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638 Access Networks ONU ONU NIU NIU ONU/NIU CO CO CO Central office Cabinet Curb Home FTTCab FTTC/FTTB FTTB/FTTH Fiber Fiber Copper RN RN RN Passive optical network (PON) Figure 11.5 Different types of fiber access networks, based on how close the fiber gets to the end user. In many cases, the remote node may be located at the central office itself. The ONUs terminate the fiber signal, and the links between the ONUs and the NIUs are copper based. to deliver broadcast services. On the other hand, it has the disadvantages of a coax- based solution, such as limited upstream bandwidth, limited reliability, and powering needed for the many amplifiers in the path. 11.3 Fiber to the Curb (FTTC) In contrast to HFC, in fiber to the curb (FTTC), data is transmitted digitally over optical fiber from the hub, or central office, to fiber-terminating nodes called optical network units (ONUs). The expectation is that the fiber would get much closer to the subscriber with this architecture. Depending on how close the fiber gets to an individual subscriber, different terms are employed to describe this architecture (see Figure 11.5). In the most optimistic scenario, fiber would go to each home, in which case this architecture is called fiber to the home (FTTH), and the ONUs would perform the function of the NIUs. For the case where ONUs serve a few homes or buildings, say, 8–64, this can be thought of as FTTC or fiber to the building (FTTB). Typically, in FTTC, the fiber is within about 100 m of the end user. In this case, there is an additional distribution network from the ONUs to the NIUs. With the fiber to the cabinet (FTTCab) approach, the fiber is terminated in a cabinet in the neighborhood and is within about 1 km of the end user. To make the FTTC architecture viable, the network from the CO to the ONU is typically a passive optical network (PON). The remote node is a simple passive device such as an optical star coupler, and it may sometimes be colocated in the
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11.3 Fiber to the Curb (FTTC) 639 central office itself rather than in the field. Although many different architectural alternatives can be used for FTTC, the term FTTC is most often used to describe a version where the signals are broadcast from the central office to the ONUs, and the ONUs share a common total bandwidth in time division multiplexed fashion. In the context of FTTC, the feeder network is the portion of the network between the central office and the remote node, and the distribution network is between the remote node and the ONUs. We will see that a variety of different types of architectures can be realized by using different types of sources at the central office combined with different types of remote nodes. Practically speaking, it is quite expensive today to transmit analog video signals over an all-fiber infrastructure; this may necessitate an analog hybrid fiber coax overlay that carries the analog video signals. The FTTC architecture is sometimes also called baseband modulated fiber coax bus (BMFCB) or switched digital video (SDV).
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This note was uploaded on 01/15/2011 for the course ECE 6543 taught by Professor Boussert during the Spring '09 term at Georgia Tech.

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Optical Networks - _11_3 Fiber to the Curb (FTTC)_128 - 638...

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