BiDi or bi-directional transmission relies on transceivers that have two different wavelengths in order to accommodate transmission in both directions on just one fiber. Unlike conventional optical transceivers which have two ports, BiDi transceivers only have one. BiDi transceivers are able to transmit signals in both directions by different center wavelength using wavelength division multiplexing (WDM), most BiDi transceivers today will utilize CWDM (coarse wavelength division multiplexing) or DWDM (dense wavelength division multiplexing).
How BiDi works
The key difference between conventional transceivers and BiDi transceivers is that BiDi transceivers are equipped with WDM couplers. These WDM couplers are able to combine or separate data transmitted over a single fiber using the different wavelengths of the light. BiDi transceivers are usually in matched pairs, one part is for the upstream (“U”) direction and its counterpart for the downstream (“D”) direction. Each of these parts would transmit at a different wavelength.
Advantages to BiDi
There are numerous benefits with BiDi being able to use a single strand of fiber to carry data in both directions rather than multiple strands.
- Double Your Network Capacity: One benefit of BiDi is that is allows you to make full use of all your fiber strands and can therefore double your network capacity. This is because one strand is used to carry information in both directions, for example if you have a six-strand cable you would be able to utilize all six stands rather than three for one direction and three for the other.
- Reliability: Other benefit is increased reliability, single strand solutions are less prone to connection errors due to fewer connections and end points.
- Cost: The most obvious benefit to BiDi however is cost. Costs associated with fiber optic cabling, labor, and material to terminate end points can all be reduced if you are working with a single fiber system. Reducing the amount of fiber needed for a system results in overall cost savings, construction costs can also be avoided since you can increase capacity of existing fibers rather than install new fiber. Finally, the reduced number of terminated fiber strands translates to fewer patch cords and patch panel ports thus a significant cost reduction.