Fiber optics can transmit data faster and over longer distances than other technologies, making it the foundation of contemporary data transmission. As a result, fiber optics are extensively used in internet services, telecom, and enterprise data center networks.
Many critical decisions come into play in the installation of fiber optic cabling, opting for single mode or multimode being one of them. This choice will have major implications for your network’s bandwidth, distance, and budget. Hence, it is vital that you have a good understanding of the differences between these two variants of fiber optic glass.
The key difference between single-mode and multimode optical fiber cables is that in the former, light rays propagate solely through one path. On the other hand, multiple light rays propagate through the waveguide at the same time in multimode optical fiber. Single-mode fiber also has a comparatively smaller core diameter than multimode fiber. Before we dig more deeply into the differences between these fiber optic glass cables, let’s better understand them.
Single-mode optical fiber
Contents
If the fiber core is so small that only a light ray at a 0° incident angle can stably pass through the fiber length without much loss, it is known as single-mode optical fiber. The core-to-cladding diameter is 9 to 125 micrometers in this situation. Single-mode optical fiber is also known as mono-mode optical fiber or uni-mode optical fiber.
Optical fiber has three parts: core, cladding, and coating or buffer. The core single-mode optical fiber is tight at the center and comprises a single fiber strand. Emitted light from the source tends to travel through this specific section. Therefore, a sharp, focused light beam like a laser is required as the optical source for the small diameter of the core. Single-mode optical fiber is known to possess minimal signal distortion owing to the transmission of just a single light ray.
Multimode optical fiber
Several light rays propagate through the fiber at the same time in multimode optical fiber. However, every light ray reflects at a certain distinctive angle during transmission. In the case of multimode optical fiber, the core-to-cladding diameter is 50-62.5 to 125 micrometers. The diameter of the core is large enough to allow several light rays to transmit through it, and it uses an LED as its optical source. As the number of light reflections created as the light passes through the core increases in the case of multimode optical fiber, it creates the ability for more data to pass through at a given time.
Understanding the differences between single-mode and multimode optical fiber
Core Diameter
Fig 1: Optical fibre core diameters
Image source: community.fs.com
The core diameter of single-mode fiber is way smaller than multimode fiber. While the former has a core diameter of 9 µm, the multimode fiber core diameter is typically between 50 µm and 62.5 µm. This allows multimode optical fiber cable to have greater “light gathering” ability and simplify connections. Due to the larger core diameter, its attenuation is greater than that of single-mode fiber. Single-mode cable has a very narrow fiber core. Therefore, the light passing through these optical cables is not reflected too often, keeping attenuation to a minimum.
Light source and wavelength
Budget-friendly light sources like VCSELs (vertical-cavity surface-emitting lasers) and LEDs (light-emitting diodes) that work at 850nm and 1300nm wavelengths are generally used in multimode fiber cables due to their large core size. On the other hand, single-mode fiber usually uses a laser or laser diode to produce light that is injected into the cable. The most frequently used single-mode fiber wavelengths are 1310 nm and 1550 nm.
Bandwidth
The bandwidth of multimode fiber is limited by its light mode. Conversely, theoretically, single-mode fiber has unlimited bandwidth as it allows just one light mode to pass through at a time. Therefore, it is a widely preferred choice in today’s fast-paced environment. Both of these optical fiber types function quite differently with regard to bandwidth. Single-mode optical fiber cable makes use of bright and strong light sources with lower attenuation. In the case of multimode optical fiber, the brightness is lower, and the attenuation is higher. Higher bandwidth and an uninterrupted experience are obviously demanded by most users, giving single-mode optical fiber an upper hand.
Color Sheath
Fig 2:Color sheath of SMF and MMF
Image source: community.fs.com
As per the standard definition under the Telecommunications Industry Association’s TIA-598-C Optical Fiber Cable Color Coding, single-mode cable is coated with a yellow outer sheath for non-military applications, and multimode fiber is coated with an orange or aqua jacket.
Transmission distance
Electronics and their light output capacity determine the transmission distance in fiber optical cables, and single-mode fiber proves to be superior in this regard as well by being capable of both short and long-distance transmission. Moreover, its transmission is not impacted by resolution quality or single bandwidth. Most of these can relay up to 10 km over a single-mode fiber cable. On the flip side, the maximum range of a multimode fiber cable tends to be between 300 and 550 meters due to its cable grading.
As multimode optical fiber supports more than one light mode and has a large core size, its fiber distance is limited by modal dispersion, which is a pretty common phenomenon in multimode step-index fiber. This does not happen with single-mode fiber.
Cost
Expenses involved are one of the key factors to consider when making any kind of purchasing decision. Naturally, you would always want to go for the option that delivers the best possible results at an affordable price. Currently, single-mode fiber has a cost advantage over its multimode variants. While they have more intricate optical processors and stronger light sources, due to their efficiency in manufacturing, single-mode fiber cables are known to be priced lower compared to multimode cables. In fact, on average, they are able to achieve 30% savings over multimode fiber.
However, it is also vital to consider that most fiber systems use transceivers responsible for combining a transmitter and receiver into a single module of fiber optic technology to receive and send over an optical network. At the moment, the price of multimode transceivers is two to three times lower than that of single-mode transceivers.
Bottom line
As multiple modes or light paths travel down a multimode fiber optic cable, it can provide high bandwidth over a short distance. All light from a pulse travels at almost the same speed and arrives at around the same time in a single-mode fiber, and hence has no effect of modal dispersion as found in multimode fiber. It is able to support higher bandwidth levels with less signal loss over longer distances and is ideal for long-haul signal transmission applications ranging from remote offices to campuses. Due to their multiple light paths, however, multimode fiber cables are good for projects that need high bandwidth over a short distance range.
You need to ponder over your specific requirements and budget limitations to select the ideal fiber optic cable for your project.
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FAQs
1. What are fiber optics used for?
Fiber optics is ideally recommended for high-performance and long-distance networking of data. The working methodology of it is to use light pulses for traveling at a faster rate. It is a revolutionary invention that has streamlined telephone, television and internet feasibility.
2. What is the difference between single-mode and multimode fiber optic cables?
The single-mode fiber is meant to propagate light only through a singular path, whereas the multimode fiber propagates several light rays through the specified waveguide. Apart from that, the core diameter of a single-mode fiber is also smaller than that of a multimode fiber. Also, the optical source for single-mode fiber is LASER, whereas LED is for multimode fiber.
3. What is the core diameter of single-mode fiber and multimode fiber?
The single-mode fiber structure is based on a simple step index, which indicates its core diameter as 9-μm and the cladding diameter as 125-μm. On the other hand, the core diameter of the multimode fiber is of two types, 50-μm and 125-μm. The cladding diameter for it is the same as that of the single-mode fiber.
4. What is the difference in light sources in single-mode and multimode fiber optic cables?
Single-mode fiber prefers using LASER as its optical source because it needs bright and strong light with low attenuation and narrow spectral width. On the other hand, multimode fiber prefers operating with LED as its light source. It is because multimode fiber has a larger core diameter, so it doesn’t need a focused beam for the transmissions.
5. What is the maximum transmission distance of single-mode and multimode fiber optic cables?
The maximum transmission distance for the single-mode optical fiber is around 6.2 miles or 10 km. But, with multimode fiber, the maximum transmission distance is much less, with just around 300 to 550 meters. It mostly happens because the potential of signal or data losses is less than that of a single-mode fiber. Thus it can send a signal to a distance 50 times greater than the maximum transmission distance of multimode fiber.