How to Maximize Capacity with BiDi Technology

If history has shown us anything in the optical communications world, it’s that fiber resources are precious and costly to install or upgrade. Whether you are pushing to maximize the capacity over your own fiber plant, or looking to reduce leased fiber expenditures, you are not alone; everyone is looking for ways to get the most out of their fiber links. So, what is the quickest and easiest way? Upgrading your optical fiber carrying capacity to jump from standard dual-fiber (duplex) transceivers to a single fiber bidirectional, or BiDi, transceiver.

What is BiDi Transmission?
BiDi transmission is the most basic and actually the initial form of wavelength division multiplexing (WDM). Today, CWDM and DWDM technology have capabilities for up to 16 or 96 channels, respectively, over a single fiber. BiDi transceivers use two wavelengths; one for upstream and one for downstream communication. Utilizing two wavelengths takes away the need for any external passive optical MUX/DMUX.

To accomplish this, a BiDi transceiver, whether it be 1G (SFP), 10G (XFP/SFP+), or 25G (SFP28), integrates a small WDM coupler (also known as a diplexer) into the transceiver package. The diplexer combines and separates upstream and downstream data from the single fiber and the transceiver itself has a single fiber port. This is in opposition to separate Tx and Rx ports you’ll see on its duplex transceiver brethren.

The advantage to BiDi transceivers is that one transceiver now has an immediate doubling of fiber capacity. For a new deployment, this can mean that half the fiber required as a data channel can now be connected over a single fiber rather than a two-fiber link. For a network upgrade, your duplex fiber can now carry two data pipes, instantly doubling capacity. This can be especially relevant as operators look to extend the life and revenue generating capacity of their installed routers and switches.

What BiDi technologies are available?
BiDi transceivers are available in a few different rates, reaches, and wavelengths, with 1G and 10G BiDis being the most common. As with their duplex counterparts, the reach capabilities of a 1G BiDitypically tops out at around ~160km, and a 10G BiDi can be capable of reaching up to ~80km. As with any component in the optical path, the internal diplexer does introduce a small amount of insertion loss into the link, so if upgrading an existing duplex connection to BiDi, talk to an optical expert and discuss any link budget concerns.

In addition to common BiDi transceivers, 25G BiDis have recently entered the market and can often be a suitable choice for delivering data in the optical portion of 5G wireless networks.

Common BiDi applications and deployments.
Now, on to the important part; where are BiDis typically deployed? From leading edge 5G wireless deployments, to utilizing the most of a legacy long-haul 1G link, a BiDi solution may be right for you!

5G deployments are putting a lot of pressure on fiber plant data carrying capacity, both in sheer bandwidth and density. Ethernet mid-haul and CPRI/eCPRI fronthaul require multiple 10G and even 25G point-to-point links to each 5G radio. Single fiber communication between the distribution unit (DU) and radio units (RU) can reduce the CAPEX expenditure in your 5G fiber network.

On the other side of the business, an existing duplex 1G or 10G span to an enterprise customer, campus, or remote community can be doubled in capacity by replacing the duplex SFP/XFP/SFP+ transceiver with two BiDis, leveraging off of your existing infrastructure with an incremental investment.

BiDi transceivers may be right for me…what’s next?
If you’re thinking that a BiDi solution may be right for your fiber infrastructure needs, Integra can help! We carry a large inventory of BiDi transceivers and have a team of engineers who can talk with you in real-time to discuss what the best implementation may be. Schedule a meeting with one of our optics experts to get more information on a BiDi rollout today!