What SFP Bidi Transceivers are available?

The SFP Transceiver

The small form-factor pluggable (SFP) is a compact, hot-pluggable transceiver used for both telecommunication and data communication applications. The form factor and electrical interface are specified by a multi-source agreement (MSA) under the auspices of the SFF Committee. It is a popular industry format jointly developed and supported by many network component vendors.

A common implementation of the transceiver is in a two fiber configuration: one for the transmission (TX) port and one for the receiving (RX) port. In this case the same frequency can be used for the transmission and reception as long as the communication channels are parallel, on separate fibers. A communication link occupies two fibers in cabling channels through data centers.

The Bidi SFP Transceiver

A special kind of transceiver is the bidirectional transceiver which implies one fiber and only one port in the transceiver. The transmission and reception functions are performed on the same fiber with the use of a pair of frequencies f1 and f2 (usually 1310nm /1490nm, other bidi SFP transceiver wavelength combinations are: 1310/1550nm, 1490/1550nm and 1510/1570nm). f1 for TX - transmission and f2 for RX - reception. Practically, from point A we have installed a transceiver which transmits TX on 1310nm towards point B on a single fiber. In point B there is a transceiver which receives RX on 1310 nm and transmits back on point A on 1490nm on the same fiber. In point A the RX frequency is listening on 1490nm. For this reason, BiDi transceivers are also referred to as WDM transceivers. 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.

The obvious advantage of utilizing 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 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.

Possible Applications with Bidi Transceivers:

• Access networks: Passive Optical Networks (PON) and Point-to-Point
• Digital video and Closed circuit television (CCTV) applications
• Inter-system communication between servers, switches, routers, OADM
• WDM Fast Ethernet Links
• SDH / STM-1, SONET / OC3
• Metropolitan area networks
• Other optic link

Bidi SFP Transceiver in FTTH / FTTB Networks

At present, the BiDi SFP is mostly used in FTTx deployment P2P (point-to-point) connection. A FTTH/FTTB (Fiber to the Home /Fiber to the Building) active Ethernet network consists of a central office (CO) connecting to the customer premises equipment (CPE). Active Ethernet networks use a P2P architecture in which each end customer is connected to the CO on a dedicated fiber. BiDi SFPs allow a bi-directional communication on a single fiber by using wavelength multiplexing (WDM), which makes CO and CPE connections simpler.

The cSFP – Dualfaser Bidi Transceiver

Compact SFPs, also known as cSFPs, enormously increase the CO port density additionally by combining two single fiber transceivers into one SFP form factor. In addition, the compact SFP will significantly reduce the overall power consumption at the CO side.

BiDi transceivers serve as an ideal and feasible solution in situations where only limited fibers or limited conduit space is available.