F. Farjady

Wavelength division multiplexing

The evolution of fiber optic technology has provided an alternative multiplexing technique called wavelength division multiplexing (WDM). In WDM, each channel is optically modulated onto a light source of a distinct wavelength. All of the wavelengths are then focused onto a single fiber by a wavelength multiplexer device. At the receiving end, the composite optical signal is spectrally filtered or dispersed into its constituent wavelengths by a demultiplexer, and each channel is detected by a photodetector.

Wavelength-tolerant optical access architectures featuring N-dimensional addressing and cascaded arrayed waveguide gratings

This paper describes two- and three-stage wavelength routed optical access networks, which offer wavelength tolerance by using coarse passband-flattened arrayed waveguide grating routers. An N-dimensional addressing strategy enables 6912 customers to be bidirectionally accessed with multi-Gb/s data using only 24 wavelengths and 1.6 nm spacing. These architectures are designed to map onto standard access network topologies, allowing elegant upgradability from legacy passive optical network (PON) infrastructures at low cost.

Reduced wavelength-count multi-stage ATM access network featuring voltage-controlled phased-array optical routers

We present a wavelength-routed optical access network, using novel passband-broadened arrayed-waveguide gratings in a three-stage architecture. By employing a multi-dimensional addressing strategy, based on spatial, wavelength and temporal multiplexing, 6912 end customers can be bi-directionally addressed with multi-Gb/s data using only 24 wavelengths with 1.6 nm spacing. Comparatively large wavelength spacing allows simple, non-temperature-stabilised WDM components to be used at the customer end. As this architecture has been designed to map onto standard access network topologies, it allows an elegant upgrade from legacy PON infrastructures, whilst also being cost effective.

Arrayed-waveguide grating passband flattening by combined phase and amplitude apodisation

We describe a novel method for arrayed-waveguide grating passband flattening based on complex aperture synthesis techniques. Typical device simulations show that Gaussian phase and amplitude exponents of 1.85 and 0.0025 respectively provide optimally flat passbands.

Phase apodisation techniques for active passband control of arrayed waveguide grating optical routers

In this paper synthetic aperture techniques for broadening and flattening the passband of the arrayed waveguide grating are discussed. Broadening by a factor of greater than 20/spl times/ is shown to be possible. It is demonstrated that by using a super-parabolic electrode with exponent P=2.1 the passband shape can be adjusted with minimum passband ripple. A novel passband flattening technique is also described which uses microlenses positioned in the output free space region. The main advantage of this approach is the enabling of active or passive control of each individual passband.

High usage optical access architecture featuring coarse space-wavelength routing

A wavelength-routed architecture is described, accessing 576 customers bi-directionally with multi-Gb/s data, and utilising only 24 wavelengths separated by 1.6 nm. Coarse routing throughout enables increased tolerance WDM components at exchange and customer premises.