Differences Between SFP, BiDi SFP and Compact SFP

As we know, a common SFP transceiver is generally with two ports, one is TX port which is used to transmit the signal, and the other one is RX port which is used to receive signals. Unlike common SFP transceiver, BiDi SFP transceiver is only with one port which uses an integral WDM coupler to transmit and receive signals over a single strand fiber. In fact, the compact SFP is a 2-channel BiDi SFP, which integrates two BiDi SFP in one SFP module. Therefore, a compact SFP is also with two ports as the common SFP.


SFP, BiDi SFP and Compact SFP Connection Methods
All SFP transceivers must be used in pairs. For common SFPs, we should connect the two SFPs which have the same wavelength together. For example, we use a 850nm SFP at one end, then we must use a 850nm SFP on the other end (shown in the figure below).


For BiDi SFP, since it transmits and receives signals with different wavelengths, we should connect the two BiDi SFPs which have the opposite wavelength together. For example, we use a 1310nm-TX/1490nm-RX BiDi SFP at one end, then we must use a 1490nm-TX/1310nm-RX BiDi SFP on the other end (shown in the figure below).


The compact SFP (GLC-2BX-D) usually uses 1490nm to transmit signal and the 1310nm to receive signal. Therefore, the compact SFP is always connected to two 1310nm-TX/1490nm-RX BiDi SFP over two single-mode fibers (shown in the figure below).


BiDi SFP and Compact SFP Applications
At present, the BiDi SFP is mostly used in FTTx deployment P2P (point-to-point) connection. A FTTH/FTTB 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 SFP allows a bi-directional communication on a single fiber by using wavelength multiplexing (WDM), which makes CO and CPE connection more simple. Compact SFP enormously increases CO port density 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 and Compact SFP Sloutions
Take FS.COM as example, the vendor provides a variety of BiDi SFPs. They can support different data rate and support transmission distance up to max 120 km that can meet the demands of today’s fiber services for carriers and enterprises.

FS SKU# Description
SKU00686G 1000BASE-BX SFP 1310nm-TX/1490nm-RX 10km Transceiver
SKU00687G 1000BASE-BX SFP 1490nm-TX/1310nm-RX 10km Transceiver
SKU00684G 1000BASE-BX SFP 1310nm-TX/1550nm-RX 10km Transceiver
SKU00685G 1000BASE-BX SFP 1550nm-TX/1310nm-RX 10km Transceiver
SKU10607Z 1000BASE-BX compact SFP 1490nm-TX/1310nm-RX 10km Transceiver

Related Article: Compatible SFPs for Ubiquiti EdgeSwitch and UniFi switch

Source: http://www.cables-solutions.com/differences-between-sfp-bidi-sfp-and-compact-sfp.html


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