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The Ultimate Guide to BiDi Transceiver

AuthorDerek

Date03/07/2022

What is BiDi? How does the BiDi transceiver work? What are the benefits of BiDi transceivers? How to choose a BiDi fiber for BiDi networks? What are the popular BiDi transceiver types? Find answers in the below paper.

What is BiDi Transceiver

What’s BiDi? The full name of BiDi is Bi-Directional. BiDi transceiver (Bi-Directional transceiver)is a kind of special optical transceiver, because it enables full-duplex data transmission via a single optical fiber while the common transceivers need dual optical fibers (Differences between full-duplex vs half-duplex vs simplex), besides, BiDi transceiver has only one simplex port for data transmitting and receiving while the common transceivers have a duplex port, one for data transmitting and the other for receiving. 

How BiDi Transceiver Works

How does the BiDi transceiver work? BiDi module enables two-way communication over one single optical fiber via the WDM filter component in the transceiver. In detail, BiDi transceivers transmit optical signals at one certain wavelength and receive optical signals at a different wavelength. That’s the bi-directional transmission. For example, in the following figure, at one side of the link, BiDi transceiver A transmits 1310nm wavelength signals and receives 1550nm wavelength signals. On the other side, BiDi transceiver B must transmit 1550nm wavelength signals and receive 1310nm wavelength signals correspondingly. That’s exactly why BiDi transceivers must be used in pairs.

How BiDi transceiver works

 

Structure Design of BiDi Transceiver

BiDi modules consist of BOSA, laser driver, and amplifier. The most important component of the BiDi optics is BOSA ( Bi-Directional Optical Subassembly). BOSA integrates the laser, detector, and WDM filter. The structure of the BOSA is shown in the following figure,

BOSA component structure of BiDi transceiver


Benefits of BiDi Transceiver

Saving Fiber Resources and Costs

Since the BiDi optics enables optical signals transmitting and receiving through a single optical fiber, the top benefit of the BiDi transceivers is saving fiber resources, which is of great value for the areas that have no extra optical fiber resources. The reduction in the use of optical fiber naturally saves the cost of cabling infrastructure. Compared with the traditional dual strand fiber bidirectional optics, the amount of fiber used per unit transmission distance of BiDi transceivers is reduced by half.

 

Convenient for Construction of Communication Facilities

Secondly, BiDi optics are convenient for construction in certain scenes. For example, in the construction scene of constructing a 4G RRU (Remote Radio Unit) station based on the previous 3G RRU station, since the previous 3G station used dual optical fiber between RRU and BBU (Building Base band Unit), if deploying BiDi transceivers, the dual strand fiber resources are able to be entirely utilized. One fiber works for the previous 3G transmission link while the other for the new 4G transmission. So, BiDi transceivers enable rapid improvement of the capacity of network links and reduce the construction cycle.

 

Easy for Management

Besides saving fiber resources, BiDi transceivers also reduce the number of ports on the fiber patch cord panel and reduce the space occupied by the tray dedicated to fiber management. Besides, BiDi transceivers are also easier for maintenance and repair in the case of an optical fiber link interrupted unexpectedly because the BiDi fibers are reduced by half compared to traditional dual strand fiber link.

 

BiDi Transceiver vs Duplex Transceiver

What are the differences between a BiDi transceiver and a traditional duplex transceiver? 

 

Firstly, from the appearance aspect, the traditional duplex transceiver connector has two ports, one is TX port for data transmitting, and the other is RX port for data receiving. In contrast, the BiDi connector has only one port for both transmitting and receiving. 

BiDi simplex connector vs traditional duplex connector

 

Secondly, the traditional duplex transceiver achieves full-duplex transmission via two fibers, whereas the BiDi transceiver only needs one fiber. The communication over a single fiber is achieved by separating the transmission wavelength with WDM technology.

 

Thirdly, the BiDi transceiver must be used in pairs while the traditional transceivers don’t. For example, a BiDi module transmitting a 1330nm signal and receiving a 1270nm signal must connect with a BiDi module transmitting a 1270nm signal and receiving a 1330nm signal.


Guides to BiDi Fiber

What optical fiber does BiDi transceiver work with? Since the BiDi transceiver has only one port for both transmitting and receiving, simplex optical fiber is the right fiber for BiDi transceiver while the traditional transceivers use duplex optical fibers. Moreover,  BiDi transceivers are generally used in the transmission distance at 10 kilometers to 120 kilometers, thus single-mode fiber should be used to work with BiDi transceivers instead of multimode fiber. A typical BiDi network link is shown in the following figure. The fiber used in the link is Simplex OS2 Single Fiber.

 

BiDi transmission over a single strand of SMF


Top BiDi Transceiver Types

BiDi SFP+ Transceiver

BiDi SFP+ transceiver is designed for 10 Gigabit Ethernet deployments. 1270nm/1310nm is the most common wavelength combination for 10G SFP+ BiDi transceivers, which is used in short/medium (10km to 60km) distance optical fiber transmission whereas 1490nm/1550nm (80km to 100km) is used in long-haul BiDi SFP+ applications.

 

BiDi SFP Transceiver

BiDi SFP module is designed for 1.25 Gigabit Ethernet deployments. 1310nm/1490nm is the most common wavelength combination for short/medium-distance (10km to 40km) BiDi networks, while 1490nm/1550nm is generally used in long-haul (80km to 120km) BiDi SFP applications.

 

40G QSFP+ BiDi Transceiver

40G QSFP BiDi transceiver is designed for 40 Gigabit Ethernet deployments. Unlike common BiDi transceivers like BiDi SFP+ and BiDi SFP with a single port, QSFP BiDi has a duplex LC connector interface and it works with two-strand duplex fiber. It consists of two 20Gbps transmit and receive channels at the wavelength range of 832-918nm. 

 

Besides, QSFP BiDi designs for short-range communication applications by working with multimode fiber. It enables a link length of 100 meters on OM3 and 150 meters on OM4/OM5 multimode fibers. 40G QSFP+ BiDi provides an efficient solution for upgrading the existing 10G duplex multimode fiber infrastructure to high-density 40G Ethernet connectivity.


Conclusion

 

The above paper has introduced BiDi transceiver definition, how it works, the benefits of BiDi, fibers for BiDi network and the popular BiDi transceiver types. QSFPTEK provides large volume BiDi transceivers including 1000BASE BiDi SFP, BiDi SFP+ and 25G SFP28 BiDi at the best price, welcome to consult via sales@qsfptek.com.

 

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