How to Choose an SFP Optical Module?

1. What is SFP?

SFP (Small Form-factor Pluggable) is a compact, hot-swappable module used in network devices such as switches, routers, and servers to provide network connectivity and is widely used in network communications. By using different interfaces and single-mode or multimode fiber depending on the distance, it enables network flexibility, facilitating deployment and maintenance, making it an indispensable component for network construction.

2. SFP Optical Module Classification

Due to different usage environments, SFP optical modules come in many different varieties. Based on the transmission medium used, they can be categorized into three main types: multimode, single-mode, and RJ45 network cables. In addition, there are fixed-distance DAC and AOC cables. These cables have a wide range of applications and provide flexible network options.

2.1 Multimode SFP Optical Modules

Multimode SFP optical modules operate at an 850nm wavelength and use multimode fiber as the transmission medium. They utilize VCSEL lasers and are suitable for short-distance transmission within 500 meters. The core diameter of multimode optical fiber is 50µm. This larger core diameter simplifies the alignment of the optical module's light source, reduces the manufacturing precision requirements, and thus lowers production costs. Therefore, multimode fiber is most suitable for short-distance transmission.

2.2 Single-mode SFP Optical Modules

Single-mode SFP optical modules operate in the 1270nm-1610nm wavelength range. Compared to multimode optical modules, single-mode modules are more expensive and come in a wider variety. They are categorized by transmission distance, including LR (10km), ER (40km), and ZR (80km). They are also categorized by operating environment, including CWDM and DWDM wavelength division multiplexing modules. Furthermore, BIDI SFP optical modules are categorized by their operating principle. This high cost brings high returns.

2.3 RJ45 Electrical Port Modules

To connect devices without SFP ports, such as PCs, the RJ45 electrical port module was developed. It uses electrical signals to transmit data over an RJ45 network cable and can be directly connected to the RJ45 port on PCs and other devices. Due to the attenuation of electrical signals by network cable materials, RJ45 electrical transceivers can only transmit up to 100 meters. Furthermore, they consume high power and have poorer compatibility than optical transceivers. Despite these drawbacks, RJ45 electrical transceivers are still widely used, as they are more convenient to use and easier to maintain than SFP optical transceivers.

2.4 SFP DAC and AOC

SFP+ DAC is a passive direct-attach copper cable. It has no active components and passively transmits electrical signals, resulting in extremely low power consumption. It is widely used in data centers. Similarly, due to the attenuation of electrical signals by copper cables, DACs cannot transmit over long distances. In production and use, they are designed to have fixed lengths, typically 1m, 2m, 3m, 5m, or 7m. SFP+ AOC (Active Direct Attach Optical Cable) differs from DAC in that it uses optical fiber to transmit optical signals. It can be thought of as a fixed-length multimode SFP optical module. However, AOCs offer higher integration, lower cost, flexible cabling, and no risk of damage from frequent fiber plugging and unplugging. Therefore, SFP AOCs are a common choice in data centers.

3. SFP Optical Module Purchasing Guide

3.1. Optical Modules vs. RJ45 Electrical Ports

Both types of modules can transmit gigabit speeds. However, for transmission distances greater than 100 meters, RJ45 electrical ports and copper cables are insufficient, requiring the use of optical modules. For transmission distances less than 100 meters, the choice between the two requires comprehensive consideration.

Data Security: Optical module signals are unaffected by electromagnetic fields, making fiber optic transmission highly resistant to electromagnetic interference and offering higher data security. This makes signals transmitted over optical fiber less susceptible to eavesdropping, thus enhancing confidentiality. Cabling Density: Network cables have thicker diameters, so they require more cabling space and are not suitable for high-density deployments. Optical fiber, on the other hand, has a smaller diameter and is well-suited for high-density deployments.

Procurement Cost: RJ45 electrical transceivers are cheaper, while optical transceivers are more expensive and require more complex maintenance, making them unsuitable for individual users.

Power Consumption and Heat Dissipation: RJ45 electrical transceivers consume more power, and the signal transmission generated by network cables also generates heat, requiring a specific cooling environment.

3.2 DAC and AOC

DAC and AOC are both common in data centers and rarely used by individual users. Their usage environments are very limited: DAC is used for short-distance interconnections within a cabinet, and AOC is used for medium-distance interconnections between cabinets. However, in data centers, DAC is in greater demand, while AOC is less popular, with most of the demand being offset by optical transceivers.

Conclusion

Through this article, I believe you have gained a basic understanding of SFP optical transceivers and a basic understanding of which SFP optical transceiver to use in which environment. YXFiber is a professional optical transceiver supplier.