Wavelength

Wavelength refers to the periodic characteristics of light waves, which are usually measured in nanometers (nm). The wavelength of a light wave determines the color of the light and its propagation characteristics in optical fiber communications. Optical modules use wavelengths for data transmission. Optical signals of different wavelengths can be transmitted simultaneously in the same optical fiber. This technology is called wavelength division multiplexing (WDM). The wavelength (λ) is the propagation distance of a light wave in space, usually expressed as the distance from peak to peak or trough to trough. In an optical module, the wavelength directly affects the signal's propagation speed, loss, bandwidth and other characteristics.

Introduction to common wavelengths in optical modules

In optical communications, according to specific applications and technologies, there are generally several common wavelengths of 950nm, 1310nm and 1550nm.

850nm is mainly used for short-distance applications, and it is transmitted through multimode optical fiber. For example, in local area networks and data centers, 850nm wavelength is often used, usually together with VCSEL technology, for optical signal transmission.

1310nm is usually used for medium and long-distance transmission, and it can use multimode and single-mode optical fibers. In multimode optical fiber, it is mainly used for short-distance transmission and is used with multimode optical fiber. In single-mode optical fiber, it is mainly used for medium-distance transmission and is used with single-mode optical fiber.

1550nm is the most common wavelength in long-distance transmission, usually used with DFB or DRB. It generally appears in scenarios such as metropolitan area networks and submarine optical fiber systems.

The above three are common wavelengths. Of course, in specific technologies or applications, narrower or custom wavelengths will be used. It all depends on factors such as your transmission distance, equipment used, compatibility, and optical fiber system.

Why these wavelengths

First, due to the attenuation characteristics of optical fibers, different types of optical fibers have different attenuation levels at different wavelengths. So when choosing a wavelength, you need to choose the wavelength with the lowest attenuation in the low-loss window of the optical fiber. For example, the two wavelengths of 1310nm and 1550nm coincide with the low-loss area, so they are more suitable for long-distance transmission.

Second, the transmission distance will cause different wavelengths to have different degrees of signal attenuation over the transmission distance due to the fiber dispersion effect and fiber nonlinearity. 1310nm and 1550nm are not easily affected by dispersion, so the transmission distance is longer. 850nm is more suitable for short-distance transmission.

In the industry, some wavelengths have also been standardized by standard organizations and regulators such as the International Telecommunication Union (ITU) and are widely adopted. This ensures interoperability and compatibility between different systems.

And these bands have been used for a long time, with fairly mature technology and reliable performance, and can be used for large-scale applications. This is also the habit of people over a long period of time. In recent years, modules with other different wavelengths have also been used, but currently these three wavelengths are the most widely used.

Advantages of each wavelength

850nm

The cost of 850nm wavelength is lower than that of the other two wavelengths, and it is more suitable for large-scale deployment because it uses mature VCSEL lasers. And it can support high-speed transmission in short distances and has low attenuation, so it has a wide range of applications.

1310nm

The smaller dispersion of 1310nm enables it to maintain good signal integrity within 10 kilometers, making it suitable for short-distance to medium-distance connections, making up for the defect that 850nm cannot transmit long distances.

1550nm

The 1550nm wavelength is more suitable for long-distance transmission. Its signal attenuation characteristics and smaller dispersion enable it to adapt to high-quality signal transmission over tens of kilometers. And 1550nm also supports wavelength division multiplexing technology, which can transmit multiple optical signals in one optical fiber, which significantly improves the utilization rate of light.

Conclusion

The three wavelengths of 850nm, 1310nm and 1550nm are widely used in optical fiber communication because they are adaptive to different application scenarios and transmission distances. 850nm is suitable for short distance and high bandwidth requirements, 1310nm has both medium distance transmission and good signal integrity, and 1550nm is an ideal choice for long distance transmission and wavelength division multiplexing. The selection of these wavelengths provides flexibility and efficiency for the construction and optimization of optical fiber communication networks.