Cascading optical multiplexing device

Abstract

An optical multiplexing device is provided comprising multiple wavelength division multiplexers cascaded together. A first one of the wavelength division multiplexers has a common port and multiple optical ports which are optically coupled to the common port. The common port may be optically coupled to a trunk line of a system employing wavelength division multiplexing, for example, a fiber-optic telecommunication system employing 4, 8, 16 or other number of multiplexed channels. The optical ports include multiple channel ports, each of which is transparent to a corresponding wavelength sub-range and reflective of other wavelengths. The second wavelength division multiplexer has a common port optically coupled to one of the optical ports of the first wavelength division multiplexer. The second wavelength division multiplexer also has multiple optical ports which are optically coupled to its common port and include multiple wavelength-selective channel ports. A waveguide, such as a fiber-optic line, can optically connect the common port of the second wavelength division multiplexer to an optical port of the first wavelength division multiplexer. The cascaded WDMs each may be optically coupled to the output of a passive coupler and a housing may be provided defining an enclosed space in which the optical multiplexing device is mounted. Optionally, additional WDMs may be cascaded with the first two WDMs in a parallel or branched formation, an in-line formation or some combination. Preferably, the channels are interleaved, such that they are removed from the multiplexed signal in certain non-sequential order. The optical multiplexing device also may employ compound interleaving wherein adjacent channels are multiplexed by different ones of the cascaded WDMs. The optical multiplexing devices can operate to add signals, remove signals or a combination of both.