John William Ballance

Optical networks for local loop applications

Some of the options for optical technology within the local loop environment are examined. In particular, passive shared access networks have been considered in some detail. These networks show great promise for delivering existing telephone services to small to medium business customers (4-30 lines) economically by the early 1990s. Extending fiber to the home will also be possible by virtue of a similar passive network infrastructure for customers requiring new broadband services beyond the single telephone line. For one-line plain old telephone service (POTS) customers, an intermediate approach of terminating the fiber network at the final network distribution point, with copper retained for the final leg, may be used prior to the provision of broadband services. A key feature of the passive optical network architecture is the use of wavelength-division multiplexing (WDM) as an upgrade strategy, allowing graceful upgrading from telephone services to multichannel high-definition television (HDTV) on gigabit/second bearers and full two-way switched broadband services employing wavelength routing across the network. >

A B-ISDN local distribution system based on a passive optical network

An experimental system that transports ATM (asynchronous transfer mode) cells through a passive optical local network (APON) is described. It distributes a 155.52 Mb/s ATM stream from an ATM node to 64 customer ends, synchronizing return cells to interleave at the exchange. A variant of the Orwell protocol is used for bandwidth control. Key features demonstrated are clock phase alignment and an exchange optical receiver design to realize a practical system. APON provides dialog service to those smaller customers that cannot be economically served using dedicated point-to-point links, permitting early economic deployment of ATM to smaller, or start up customers.<<ETX>>

An experimental broadband and telephony passive optical network

An experimental passive optical network that demonstrates the integrated delivery of telephony and broadband services to a variety of business and residential customers over a typical local loop is described. Telephony is provided over a 112-way split at 1300 nm, and broadband services (asynchronous transfer mode and single-channel video at 155 Mb/s, and 2.2 Gb/s 32-channel video) are provided over a 28-way split. Two approaches to the addition of broadband services are used: coarse-grained WDM (wavelength-division multiplexing) with 20-nm channel spacing in the 1300-nm window, and high-density WDM with 1-nm spacing in the 1500-nm window. Optical technology solutions are described for providing different levels of service to various customer types, including a single-mode wavelength multiplexer with 1-nm channel spacing, a hybrid integrated demultiplexer/receiver with 20-nm channel spacing, and a tunable optical filter with 0.6-nm FWHM (full-width at half-maximum) bandwidth.<<ETX>>