Wavelength

What Is the Wavelength?

In physics and optics, wavelength refers to the distance between two consecutive points of a wave in the same phase. It is commonly denoted by the Greek letter lambda (λ). Wavelength is a fundamental property of waves and is used to describe various types of waves, including electromagnetic waves such as light.

In the context of light, wavelength specifically refers to the distance between two consecutive peaks or troughs of the light wave. It is measured in units of length, such as meters (m), nanometers (nm), or micrometers (μm).

What Are the Commonly Wavelengths in Optical Fibers？

In optical fiber communications, several wavelengths are commonly used depending on the specific application and technology. Here are the most commonly used wavelengths in optical fibers:

850 nm: This wavelength is primarily used in multimode fiber for short-distance applications, such as local area networks (LANs) and data centers. It is often used with VCSEL (Vertical-Cavity Surface-Emitting Laser) technology.

1310 nm: This wavelength is used in both single-mode and multimode fibers. In single-mode fibers, it is commonly used for long-distance communication and is compatible with lower-cost laser sources. In multimode fibers, it is used for intermediate-range transmission. The difference between the wavelength 1300nm and 1310nm is only the difference in the customary name.

1550 nm: This wavelength is predominantly used in single-mode fibers for long-distance communication. It is the most widely used wavelength for long-haul and submarine fiber optic systems. It is compatible with high-performance laser sources, such as distributed feedback (DFB) or distributed Bragg reflector (DBR) lasers.

It's important to note that these are general wavelength ranges, and specific applications or technologies may utilize narrower bands or custom wavelengths. The choice of wavelength depends on factors such as transmission distance, available equipment, compatibility, and the specific requirements of the fiber optic system.

Why Are These Wavelengths Chosen?

The selection of specific wavelengths in optical fibers is driven by several factors, including the characteristics of the fiber, transmission requirements, available technology, and compatibility with existing systems. Here are the main reasons why these wavelengths are commonly chosen:

1. 1. Fiber Attenuation Characteristics: Different types of optical fibers have varying levels of attenuation at different wavelengths. The chosen wavelengths are typically within the low-loss windows of the fiber, where attenuation is minimized. For example, in single-mode fibers, the 1310 nm and 1550 nm wavelengths coincide with the low-loss regions, making them ideal for long-distance transmission.

2. 2. Optimal Laser Sources: The availability and performance of laser sources play a significant role in wavelength selection. The chosen wavelengths are often compatible with commercially available laser diodes that provide high performance and reliability. Laser diodes emitting at 850 nm, 1310 nm, and 1550 nm are widely available and cost-effective for their respective applications.

3. 3. Transmission Distance: Different wavelengths exhibit varying levels of signal degradation over distance due to fiber dispersion effects and fiber nonlinearities. Longer wavelengths, such as 1310 nm and 1550 nm, are less susceptible to dispersion, making them suitable for long-distance transmission. Shorter wavelengths, like 850 nm, are often used for shorter-range applications where dispersion is less of a concern.

4. 4. Compatibility with Existing Infrastructure: In many cases, the choice of wavelength is influenced by compatibility with existing fiber optic infrastructure. Upgrading or expanding an existing network may require maintaining compatibility with the installed fiber and equipment, which could be optimized for specific wavelengths.

5. 5. Standardization: Certain wavelengths have been standardized and widely adopted within the industry. Standards organizations and regulatory bodies, such as the International Telecommunication Union (ITU), define specific wavelength bands for various applications to ensure interoperability and compatibility between different systems.

6. 6. Multiplexing Techniques: Wavelength-division multiplexing (WDM) technology, which enables multiple wavelengths to be simultaneously transmitted over a single fiber, relies on specific wavelength spacing and compatibility. The chosen wavelengths, such as 1310 nm and 1550 nm, are widely adopted in WDM systems to increase the capacity and efficiency of fiber optic networks.

It's important to note that the choice of wavelength is not limited to the ones mentioned above. Depending on specific applications, custom wavelengths or wavelength bands can be utilized to meet specific requirements, such as specialized scientific applications or specific network architectures.