What Is Single Mode Fiber?
Single mode fiber (SMF) is a type of fiber optic cable that only allows one light mode to transmit at a time. Generally, single mode cable has a narrow core diameter of 8 to 10µm (micrometers), which can propagate at the wavelength of 1310nm and 1550nm.
Modes of light can only propagate through single mode fiber optic cables due to their small core diameters. As a result, the amount of light reflection that occurs as light passes through the core is reduced, reducing attenuation and allowing the signal to propagate further.
Signals such as Cable TV, Internet, and telephone are generally carried by single mode fibers, which are wrapped together into a huge bundle. Single mode fiber is used over long distances, however, at high transmission speeds, the cable and equipment used for single mode fiber are more expensive compared to multimode fiber (MMF).
Single Mode Fiber Types: OS1 vs OS2
It’s of great significance to figure out the difference between OS1 and OS2 when conducting deployments. The specification table below will present the differences between them clearly.
| OS1 | OS2 | |
|---|---|---|
| Standards | ITU-T G.652A/B/C/D | ITU-T G.652C/G.657.A1 (part) |
| Cable Construction | Tight Buffer | Loose Tube |
| Application | Indoor | Outdoor |
| Attenuation | 1.0db/km | 0.4db/km |
| Max. Distance | 10 km | 200 km |
| Price | Low | High |
What are the Pros and Cons of Single Mode Fiber?
Pros:
- Transmission distance: single mode fiber supports a greater distance than multimode fiber because of its lower attenuation. For example, multimode fiber generally has a reach of several hundred meters, whereas single mode fiber has the potential to reach 200 km.
- Bandwidth capacity: single mode fiber supports high bandwidths and high speeds up to 10Gbps for about 10Km, compared to a multimode fiber optic cable.
- Data dispersion: single mode fiber only transmits light of one mode, causing no modal dispersion.
- Attenuation: the fiber core in the single-mode fiber optic cable is relatively small, so very little light is reflected as it passes through, minimizing attenuation.
Cons:
- Stricter technology: because of the smaller core diameter, it is more difficult to manufacture and handle SMFs than MMFs.
- High cost: single mode fiber devices are more expensive than multimode fiber devices because single mode fiber typically uses solid-state laser diodes.
- Requires much tighter tolerances: it is difficult to couple light into a single mode fiber than into a multimode fiber because of the smaller fiber core diameter inside the SMF. The smaller cores (8-10 µm) require much tighter tolerances than coupling light into the larger cores (62.5/50 µm) of multimode fibers.
Applications of Single Mode Fiber Optic Cables
Single mode fiber applications could be divided into four main situations listed below according to different categories.
| Categories | Application Scenarios |
|---|---|
| Traditional/standard single mode fiber | Metropolitan and access networks |
| Negative non-zero dispersion shifted fiber | Metropolitan and medium distance networks |
| Positive non-zero dispersion shifted fiber | Long-haul and high-data-rate metropolitan networks |
| High positive non-zero dispersion shifted fiber | High-speed, high-capacity, unrepeatered submarine networks |
In addition, single mode fiber has a wide range of application in fiber optic components or equipment making such as single mode fiber optic adapter, fiber optic attenuator, pigtail and patch cords. For example, the indoor single mode fiber cable can be produced as fiber pigtails or patch cords to connect with fiber optic equipment of single mode type.
Summary
From all the above, single mode fiber is necessary and effective for network building in different situations. And the use of single mode fiber optical cable is the best way to get rid of modal dispersion over long distances. Therefore, it is very popular to use single mode fiber in backbone systems.
Related Article:
