The light we are most familiar with is, of course, the light we can see with our naked eyes. Our eyes are sensitive to violet light with wavelengths between 400nm and 700nm red light. But for optical fibers carrying glass fibers, we use light in the infrared region, which has longer wavelengths, causes less damage to the fiber, and is invisible to the naked eye. This article will tell you more about fiber wavelengths and why you should choose these wavelengths.
Wavelength Basics
Light is defined by its wavelength. Wavelength is a number that represents the spectrum of light. Each frequency, or color, of light, has a wavelength associated with it. Wavelength and frequency are related. Shortwave radiation is identified by its wavelength and longwave radiation, on the other hand, is identified by its frequency.
Generally, 800 to 1600nm, but the most commonly used wavelengths in optical fiber are 850nm, 1300nm, and 1550nm. The wavelengths of 850nm and 1300nm are suitable for multimode fiber, while the wavelengths of 1310nm and 1550nm are best used for single-mode fiber. The only difference between wavelengths 1300nm and 1310nm is their customary name. Light propagation in optical fibers also includes lasers and light-emitting diodes. Lasers are used in single-mode devices with wavelengths of 1310nm or 1550nm, while LEDs are used in multi-mode devices with wavelengths of 850nm or 1300nm.
Types of Wavelengths in Optical Fiber
In optical fiber communication, three main wavelength bands are commonly used: the O-band (original), the E-band (extended), and the U-band (ultra-extended). Each band has unique characteristics and applications, contributing to the versatility of optical fiber networks.
O-band (Original Band)
The O-band, with wavelengths ranging from approximately 1260 nm to 1360 nm, was the first wavelength band used in optical fiber communication. It laid the foundation for early optical communication systems.
E-band (Extended Band)
To meet the growing bandwidth requirements, E-band was launched, covering wavelengths from approximately 1360 nm to 1460 nm. The expanded frequency band can increase the data capacity and better performance of optical communication systems to meet data-intensive applications.
U-band (Ultra-Extended Band)
The ultra-extended band, or U-band, represents wavelengths from approximately 1460 nm to 1650 nm. This band further expanded the capacity of optical fiber communication systems, enabling the transmission of vast amounts of data over long distances with minimal signal degradation. The U-band is particularly crucial for long-haul and submarine communication links.
Wavelength Division Multiplexing (WDM)
One of the key innovations that revolutionized optical fiber communication is Wavelength Division Multiplexing (WDM). WDM allows multiple wavelengths, or channels, to coexist on a single optical fiber simultaneously. This technique significantly increases the data-carrying capacity of the fiber, enabling the transmission of multiple signals independently.
WDM comes in two main flavors: Coarse Wavelength Division Multiplexing (CWDM) and Dense Wavelength Division Multiplexing (DWDM). CWDM uses fewer, more widely spaced wavelengths, making it suitable for shorter-distance applications. On the other hand, DWDM employs closely spaced wavelengths, enabling higher data capacities and longer-distance transmissions.
Why Choose These Wavelengths?
When choosing a transmission wavelength, the goal is to send the most data over the furthest distance with the least signal loss. The loss of signal strength during transmission is called attenuation. The most commonly used wavelengths in optical fiber are 850nm, 1300nm, and 1550nm. Why do we select these three wavelengths of light? This is because the optical signals of these three wavelengths have the smallest loss when transmitted in optical fibers. They are therefore best suited as available light sources for transmission in optical fibers. There are two aspects of glass fiber loss: absorption loss and scattering loss. Absorption loss mainly occurs at a few specific wavelengths we call the “water zone”, mainly due to the absorption of trace amounts of water droplets in the glass material. The rebound of atoms and molecules on the glass is the main cause of scattering.
Due to the influence of wavelength, the scattering of long waves is much smaller. From the table below we can see three low-absorption regions and a curve in which scattering decreases as the wavelength length increases. As you can see, the absorption is almost zero in these three wavelength regions.
The Importance of Wavelength in Optical Fiber
Confirm Signal Transmission
Wavelength plays a vital role in determining the transmission capabilities of a fiber optic system. Different wavelengths of light can be used to transmit different types of signals simultaneously on a single fiber. This technology, called wavelength division multiplexing (WDM), makes efficient use of fiber optic infrastructure, allowing multiple signals to be transmitted simultaneously on the same fiber.
Maximize Bandwidth
By utilizing different wavelengths, fiber optic systems can achieve increased bandwidth capacity. Each wavelength can be assigned to carry a different signal, effectively doubling the fiber’s data-carrying capacity. This ability to transmit multiple wavelengths simultaneously significantly enhances the overall bandwidth potential of fiber optic networks.
Minimize Signal Interference
Wavelength also plays a vital role in minimizing signal interference in fiber optic systems. By using different wavelengths for different signals, each wavelength can be isolated and separated, reducing the potential for crosstalk and signal degradation. This ensures the integrity and quality of transmitted data, making fiber optic a reliable and robust communications medium.
Light Source Compatibility and Fiber Component Design
Fiber optic systems are designed to operate efficiently within a specific wavelength range. Therefore, the choice of light source should be consistent with the operating wavelength range of the optical fiber network. The design and performance of fiber optic components such as lasers, detectors, and amplifiers also depend heavily on wavelength considerations.
Conclusion
The wavelength of optical fiber is a fundamental aspect that underpins the design, performance, and capabilities of modern communication networks.
From the early days of the O-band to the current exploration of new wavelength bands, the evolution of optical fiber communication reflects our relentless pursuit of faster, more reliable, and more efficient ways to connect the world. Whether it’s for global telecommunications networks, data centers, or cutting-edge applications like quantum communication, the wavelength of optical fiber remains a key enabler of the digital age.
