In the world of fiber optic communication, the selection of light wavelength is like radio frequency tuning and channel selection. Only by selecting the right “channel” can the signal be transmitted clearly and stably. Why do some optical modules have a transmission distance of only 500 meters, while others can span over hundreds of kilometers? The mystery lies in the ‘color’ of that beam of light – more precisely, the wavelength of the light.
In modern optical communication networks, optical modules of different wavelengths play completely different roles. The three core wavelengths of 850nm, 1310nm, and 1550nm form the fundamental framework of optical communication, with clear division of labor in terms of transmission distance, loss characteristics, and application scenarios.
1.Why do we need multiple wavelengths?
The root cause of wavelength diversity in optical modules lies in two major challenges in fiber optic transmission: loss and dispersion. When optical signals are transmitted in optical fibers, energy attenuation (loss) occurs due to absorption, scattering, and leakage of the medium. At the same time, the uneven propagation speed of different wavelength components causes signal pulse broadening (dispersion). This has given rise to multi wavelength solutions:
•850nm band: mainly operates in multimode optical fibers, with transmission distances typically ranging from a few hundred meters (such as~550 meters), and is the main force for short distance transmission (such as within data centers).
•1310nm band: exhibits low dispersion characteristics in standard single-mode fibers, with transmission distances up to tens of kilometers (such as~60 kilometers), making it the backbone of medium distance transmission.
•1550nm band: With the lowest attenuation rate (about 0.19dB/km), the theoretical transmission distance can exceed 150 kilometers, making it the king of long-distance and even ultra long distance transmission.
The rise of wavelength division multiplexing (WDM) technology has greatly increased the capacity of optical fibers. For example, single fiber bidirectional (BIDI) optical modules achieve bidirectional communication on a single fiber by using different wavelengths (such as 1310nm/1550nm combination) at the transmitting and receiving ends, significantly saving fiber resources. More advanced Dense Wavelength Division Multiplexing (DWDM) technology can achieve very narrow wavelength spacing (such as 100GHz) in specific bands (such as O-band 1260-1360nm), and a single fiber can support dozens or even hundreds of wavelength channels, increasing the total transmission capacity to the Tbps level and fully unleashing the potential of fiber optics.
2.How to scientifically select the wavelength of optical modules?
The selection of wavelength requires comprehensive consideration of the following key factors:
Transmission distance:
Short distance (≤ 2km): preferably 850nm (multimode fiber).
Medium distance (10-40km): suitable for 1310nm (single-mode fiber).
Long distance (≥ 60km): 1550nm (single-mode fiber) must be selected, or used in combination with an optical amplifier.
Capacity requirement:
Conventional business: Fixed wavelength modules are sufficient.
Large capacity, high-density transmission: DWDM/CWDM technology is required. For example, a 100G DWDM system operating in the O-band can support dozens of high-density wavelength channels.
Cost considerations:
Fixed wavelength module: The initial unit price is relatively low, but multiple wavelength models of spare parts need to be stocked.
Tunable wavelength module: The initial investment is relatively high, but through software tuning, it can cover multiple wavelengths, simplify spare parts management, and in the long run, reduce operation and maintenance complexity and costs.
Application scenario:
Data Center Interconnection (DCI): High density, low-power DWDM solutions are mainstream.
5G fronthaul: With high requirements for cost, latency, and reliability, industrial grade designed single fiber bidirectional (BIDI) modules are a common choice.
Enterprise park network: Depending on distance and bandwidth requirements, low-power, medium to short distance CWDM or fixed wavelength modules can be selected.
3.Conclusion: Technological Evolution and Future Considerations
The optical module technology continues to iterate rapidly. New devices such as wavelength selective switches (WSS) and liquid crystal on silicon (LCoS) are driving the development of more flexible optical network architectures. Innovations targeting specific bands, such as the O-band, are constantly optimizing performance, such as significantly reducing module power consumption while maintaining sufficient optical signal-to-noise ratio (OSNR) margin.
In the future network construction, engineers not only need to accurately calculate the transmission distance when selecting wavelengths, but also comprehensively evaluate power consumption, temperature adaptability, deployment density, and full lifecycle operation and maintenance costs. High reliability optical modules that can operate stably for tens of kilometers in extreme environments (such as -40 ℃ severe cold) are becoming a key support for complex deployment environments (such as remote base stations).
Post time: Sep-18-2025