SFP (small form factor pluggable) modules and BiDi (bidirectional) SFP are among the most commonly utilized optical transceiver types. BiDi is essentially a variation of SFP, offering distinct functionalities. SFP transceivers are compact modules employed in voice and data applications. They typically feature separate ports for transmission (TX) and reception (RX), with parallel fibers dedicated to each function. Conversely, BiDi transceivers utilize a single optical fiber and port for both transmitting and receiving data.

What is the SFP Transceiver?

The Small Form-Factor Pluggable (SFP) is a compact and hot-swappable transceiver used in both telecommunication and data communication applications. Its size and electrical interface are determined by a Multi-Source Agreement (MSA) supported by the SFF Committee. It serves as a widely adopted industry standard developed collaboratively and endorsed by multiple network components. A typical SFP transceiver setup involves a dual-fiber configuration, with one fiber dedicated to transmission (TX) and the other for reception (RX). In this setup, the same frequency can be utilized for both transmitting and receiving data, provided that the communication channels operate independently on separate fibers. Within data center cabling channels, a communication link typically occupies two fibers.

What is the BiDi SFP Transceiver?

Another type of transceiver is the bidirectional (BiDi) transceiver, which operates using a single optical fiber and a single port. Both transmission and reception functions occur on the same fiber using a pair of frequencies, typically denoted as F1 and F2 (commonly 1310nm/ 1490nm, though other wavelength combinations such as 1310/1550nm, 1490/1550nm, and 1510/1570nm are also used in BiDi SFP transceivers). F1 is employed for transmitting (TX), while F2 is utilized for receiving (RX). Actually, a BiDi transceiver is installed at point A, sending TX signals at 1310nm through a single optical fiber to point B. At point B, another BiDi transceiver receives the 1310nm signals and transmits back to point A at 1490nm over the same fiber. At point A , the received signals are monitored at 1490nm. This characteristic of BiDi transceivers leads to them being alternatively referred to as Wavelength Division Multiplexing (WDM) transceivers. WDM couplers, also known as duplexers, facilitate the coupling and separation of data transmitted through a single optical fiber based on the wavelength of light.

What are the Differences Between SFP and BiDi SFP?

While both common SFP modules and BiDi SFP serve to conserve space and streamline wiring, they diverge significantly in several key aspects. Here are the primary distinctions between BiDi SFP and standard SFP modules:

Number of Ports and Fiber Usage

SFP: A typical SFP transceiver module features two distinct ports—one for transmitting (TX) and one for receiving (RX)—enabling communication over two fiber strands within an optical cable.

BiDi SFP: Unlike traditional SFP modules, BiDi SFP utilizes wavelength division multiplexing (WDM) technology to enable bidirectional transmission over a single fiber optic cable. This means it only requires one port for both transmitting and receiving signals. Additionally, BiDi SFP modules must be deployed in pairs, and their single-fiber usage allows for more modules to be used in the same switch.

Data Rates and Wavelengths

SFP: In SFP modules, separate transceiver and receiver ports are required. Data rates vary from 10/100/1000Mbps to 100Mbps, 1000Mbps, 10Gbps, and beyond. Transmission distances can extend up to 100km. These devices are hot-pluggable and also referred to as mini-GBIC.

BiDi SFP: BiDi SFP modules achieve bidirectional data transfer by utilizing different wavelengths for upstream and downstream data on the same port and cable. Data rates range from 1G to 10G, with support for transmission distances of up to 120km.

Cost and Compatibility

SFP: SFP modules are cost-effective due to their simple design compared to BiDi SFP. They offer compatibility with both Ethernet and optical fiber cables, featuring connectors for both types. They are versatile, compatible with various communication standards like SONET, Gigabit Ethernet, Fiber Channel, and those compliant with the Multi-Source Agreement (MSA), offering broad compatibility alongside affordability.

BiDi SFP: BiDi SFP modules are pricier than standard SFP modules primarily due to the integration of WDM technology. Their design adherence to specific standards might result in compatibility issues with cables and connectors of communication standards other than fiber optic.

Applications

SFP: Standard SFP modules compliant with the Multi-Source Agreement (MSA) find extensive use across various applications, including short-haul and long-haul links, Ethernet, and other protocols, owing to their cost-effectiveness and compatibility. They are particularly reliable for high-bandwidth applications requiring full-duplex communication. Notably, these modules can effectively integrate into blended networks, where fiber optics are employed to extend existing copper cable networks.

BiDi SFP: BiDi SFP modules are ideal for point-to-point connections where reducing fiber costs or dealing with limited fiber resources is crucial. However, they come with limited wavelength options and compatibility despite their higher cost. Despite the advantages of BiDi SFP, Many business networks lack equipment supporting BiDi protocols, making standard SFP modules the more commonly used option.

How to Choose the Right SFP Module?

Choosing the appropriate transceiver module depends largely on your network requirements.

• Evaluate your network requirements and future business expansion plans, considering factors like single mode or multimode networks, transmission distance, data rates, etc.

• If you’re expanding your existing network and incorporating fiber optics, standard SFP transceiver modules are recommended to avoid compatibility issues that BiDi modules may present.

• If you need to minimize fiber optic wiring and have space limitations, BiDi modules may be suitable, but ensure your network is fully fiber optic and that your equipment is compatible. Verify the fiber type and wavelength compatibility.

• Regardless of the module type chosen, prioritize scalability to accommodate future expansions.

• Consider the expected cost savings and overall budget, noting that BiDi SFP modules require a significant investment.

• Pay attention to switch compatibility, particularly regarding SFP switch ports. Ensure compatibility with RJ45 connectivity, fiber optic requirements, PoE Switches, and any other essential features for your network.

If you plan to install a new fiber optic network, replace the legacy one, or opt for a blend of copper and fiber, you will require not only SFP transceiver modules but also other compatible network devices such as media converters, modems, SFP switches, and more. We offer a variety of SFP modules. For any further information you require, feel free to contact the HOLIGHT team via email sales@holightoptic.com.