Fibre optic networking has traditionally required two fibres to accomplish full duplex communications. With recent technical advancements it is now possible to achieve full duplex communications over a single fibre by using two separate optical wavelengths.
As a result of cost reduction in bi-direction, dual wavelength transceiver has now made it possible to use Single Fibre technology in an access network with minimal cost increase over equivalent dual fibre equipment.
For operations that require increased capacity – without the capital expenditure headache – the existing single fibre network could be the solution to boost capacity while maintaining resilience and high reliability.
Single strand fibre has numerous benefits including:
- Instantly doubles network capacity: Single strand fibre increases the capacity of the fibre by simultaneously operating at more than one wavelength, transmitting and receiving on a single strand.
- Increases reliability: By decreasing the number of connections or end points in a network, the number of potential issues is decreased. A customer may also choose to use single fibre to increase redundancy in the network.
- Decreases cost: The costs associated with installation and maintenance of the fibre are reduced. By decreasing the total amount of fibre, the result is a reduction of overall labour costs and conversely construction costs are avoided since you are increasing the capacity of existing fibre versus installing additional fibre.
The principle of Single Fibre Working (‘SFW’) technology is that it allows simultaneous communication in both directions at different wavelengths. A simple Wavelength Division Multiplexing (‘WDM’) system as depicted below shows signal wavelengths are widely spaced and are also referred as Broad WDM.
A SFW link also can be augmented or upgraded with additions of more wavelengths by deploying Coarse Wavelength Division Multiplexing (CWDM) or Denes Wavelength Division Multiplexing (DWDM) technologies.
Coarse Wavelength Division Multiplexing (CWDM) is a robust technology able to create 18 independent channels with 20nm spacing, typically used for un-amplified (passive) transmission up to 200km.
To further increase capacity, Dense Wavelength Division Multiplexing (DWDM) can be employed. DWDM wavelengths are typically only 1.6nm wide) and require much more sophisticated technology to maintain the assigned wavelengths.
Example of a Single Fibre Working 4 Channel, CWDM System
Below is a 4-Channel CWDM system operating on a single fibre with data rate from 155Mb/s to 10Gb/s. The transmission distance can be up to 200km.
Note: Optical receivers for SFW applications are wavelength insensitive. In the above example, a 1470nm transceiver is used to transmit at 1490nm and receiver at 1490nm at ‘A’ end and 1490nm transceiver at ‘B’ end.
The following table compares the achievable capacity increase and costs for the different SFW technologies.
To meet future needs, Single Fibre Technologies offers a unique, cost effective solution when increasing capacity compared with duplex transmission technology.