Fiber to the Cabinet or FTTCab

What used to be called Fiber to the Node or FTTN is now called Fiber to the Cabinet or FTTCab in the ITU standards. The acronym is obviously quite close to that for Fiber to the Curb or FTTC. Luckily, both of these architectures are related with the main difference being exactly where in the OutSide Plant (OSP) the fiber-fed DSLAM is installed. FTTCab has the Digital Loop Carrier (DLC) and Digital Subscriber Line Access Multiplexer (DSLAM) installed installed at a local loop concentration point known as the Feeder Distribution Interface or FDI and typically serving several hundred subscribers. FTTC has the DLC and DSLAM installed at the curb, and it typically serves 8-12 subscribers from a single installation.

A typical network architecture for FTTCab is shown below. A FTTC architecture would have fiber from the Wire Center all the way to the Distribution/Drop interface, which is typically installed at the curb.

The picture below is a FTTCab installation near my house. The rear beige cabinet is a Digital Loop Carrier (DLC) system, which houses telephony electronics. The two beige cabinets in front of the DLC house adjunct DSLAMs providing DSL services. The green cabinet to the right is the Feeder Distribution Interface, which provides copper pair concentration. FDI concentration is typically 2 distribution pairs for each feeder pair. In this case, the feeder copper pairs are only a few feet in length since they are terminated at the two DSLAM cabinets shown in the picture.

DLC and FTTCab

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