Optical Multiplexing

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There are many options available to the System Designer when planning an optical link.  There are a number of optical multiplexing methods available and the choice depends upon the number of point to point signals to transport and the availability of fibre cores.  The widespread adoption of the interchangeable SFP often means the upgrade path is simply an SFP change and the addition of an appropriate passive multiplexer.  Bidirectional links also prove very cost effective using this method. The links are agnostic to the signals being transported and can be used with electrical TDM (Time Division Multiplexing) to further increase the signal density.

WDM (Wave Division Multiplexing) is a passive technology for the multiplexing or de-multiplexing of two optical wavelengths onto or from a single fibre optic cable.  WDM typically operates with 1310 and 1550 nm wavelengths on singlemode fibres or with 850 and 1310 nm wavelengths on multimode networks.  As standard transmitters and receivers are used, overlaying an extra wavelength via WDM proves to be a very cost effective solution for system designers looking to increase capacity on existing networks.  This can be particularly true in legacy multimode networks.  Variations of the BC2 are available which house 1 or 2 WDM units on a single BC Series card.

WDM - 2 wavelengths onto 1 fibre
WDM – 2 wavelengths onto 1 fibre – click to enlarge

CWDM (Coarse Wave Division Multiplexing) is a technique to combine up to 18 individual wavelengths onto a single fibre according to ITU-T G.694.2.  Wavelengths can be combined in groups of up to 4 or 8 wavelengths and can be bidirectional.  Each device in the range is passive and allows for the multiplexing or de-multiplexing of different optical wavelengths onto or from a singlemode fibre optic cable.  Each BC-4 or BC-8 unit will combine or separate signals with a 20 nm wavelength spacing based around the ITU G.694.2 grid specifications.  Adding additional BC-4 or BC-8 cards allows the system to transmit a total of 16 independent wavelengths on a single fibre, proving to be a very cost effective solution for system designers working with third party leased fibres or in Outside Broadcast.

BC4 - 4 channel CWDM mux
BC4 – 4 channel CWDM mux – click to enlarge

The BC-4 and BC-8 units occupy a single slot in the BC Series 19” rack-mounting frames.
Each module is designed for applications where space is at a premium, ideal for portable OB systems when fitted in the BC160/BC160P units.
The BC-8D occupies two slots in the BC Series 19″ rack-mounting frames and is ideal for cost effective installations where space is not critical.
The BC160P 19” 1RU frame is specifically intended to house passive optical modules including splitters, WDM and CWDM devices.  When used in combination with the active frames they produce ultra compact optical multiplexing and distribution systems.

8 channel mux
8 channel mux

Optical Splitters and Switches can be used alongside the interface products to produce complete optical networks.  Splitters can be supplied that allow passive optical distribution in 2, 4 or 8 directions.  They can also be used to distribute sync signals optically within a facility or to provide diverse routing between buildings for example.  
The BC2x1SW allows for optical switching between a main and redundant fibre path.
The BC1x2SW and a dedicated frame provide a manual switchover from a prime location to a disaster recovery position.

DWDM (Dense Wave Division Multiplexing) is an optical multiplexing technology to further increase the number of wavelengths on a single fibre by reducing the spacing between adjacent wavelengths.  Please contact the Sales Office to discuss the current range of DWDM SFPs we supply.

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