Optics Telecom

Many modern optical transceivers utilize two fibers to transmit data between switches, firewalls, servers, routers, etc. One fiber is dedicated to receiving data from networking equipment, and the other is to transmit data to the networking equipment. Nowadays, a new optical transceiver technology is available which allows transceivers to both transmit and receive data to/from interconnected equipment through a single optical fiber. This technology now has led to the development of Bi-Directional transceivers, or BiDi transceivers for short.

BiDi optical transceiver is a compact optical transceiver module used in optical communications for both telecommunication and data bidirectional communications applications. It interfaces a network device mother board, like a switch, router or similar device, to a fiber optic or unshielded twisted pair networking cable. It is a popular industry format supported by several fiber optic component vendors. In the industry there are several synonyms for Bidi optics, such as: Bi-directional optics, BX-D/BX-U, WDM and so on. Specifically, the SFP-1G-BX-D and SFP-1G-BX-U are for the 1G. BIDI 1G optics are a small form factor pluggable module for single mode Fast Ethernet, Gigabit, Fiber Channel, SDH/SONET applications. BiDi SFP can be produced either with SC or LC simplex port, that is used both transmission and receiving. The most typical wavelength combination is 1310/1490, 1310/1550, 1490/1550 and 1510/1570. For a link you need 2 different optics, one that sends 1310nm and receives 1490nm and the other side of the fiber, which has a Bidi optic which sends 1490nm and receives 1310nm. In most cases these wavelengths are mentioned as Tx (transmitting) and Rx (receiving) on the label of the optic.

The primary difference between BiDi transceivers and traditional two-fiber fiber optic transceivers is that BiDi transceivers are fitted with wavelength division multiplexing (WDM) couplers, also known as diplexers, which combine and separate data transmitted over a single fiber based on the wavelengths of the light. For this reason, BiDi transceivers are also referred to as WDM transceivers. To work effectively, BiDi transceivers must be deployed in matched pairs, with their diplexers tuned to match the expected wavelength of the transmitter and receiver that they will be transmitting data from or to.

For example: If paired BiDi transceivers, like GLC-BX-U and GLC-BX-D branded by Cisco, are being used to connect Device A (Upstream) and Device B (Downstream), as shown in the picture below, then:

• Transceiver A's diplexer must have a receiving wavelength of 1490nm and a transmit wavelength of 1310nm
• Transceiver B's diplexer must have a receiving wavelength of 1310nm and a transmit wavelength of 1490nm

The obvious advantage of choosing BiDi transceivers, such as SFP+ BiDi or SFP BiDi transceivers, is the reduction in fiber cabling infrastructure costs by reducing the number of fiber patch panel ports, reducing the amount of tray space dedicated to fiber management, and requiring less fiber cable. While BiDi transceivers, or WDM transceivers, cost more to initially purchase than traditional two-fiber transceivers, they utilize half the amount of fiber per unit of distance. For many networks, the cost savings of utilizing less fiber is enough to more than offset the higher purchase price of BiDi transceivers.

Fiberstore offers a large selection of BiDi transceivers branded by many famous companies, like Cisco, Juniper, and HP. BiDi SFP transceivers in Fiberstore can be produced either with SC or LC simplex port. And the typical wavelength combinations, such as 1310/1490, 1310/1550 and 1490/1550, are all available. For example, J9142B and J9143B branded by HP are paired BiDi SFP transceivers, using 1310nm/1490nm transmitter and 1490nm/1310nm receiver.