Light wave and data transfer
Light wave and data transferDate of publication: 09-01-2026 🕒 7 min read
Optical fiber, also referred to as an optical cable (in English: fiber optic cable), is a type of transmission medium that uses light pulses for high-speed data transfer over long distances with relatively low signal loss. This is made possible by guiding a beam of light through the core of the fiber. Due to its high bandwidth compared to traditional cables, optical fiber is gaining popularity and is used in areas such as telecommunications, medicine and industry.
- Construction of an optical cable
- Classification of optical fibers by structure
- Fiber categories
- Most popular types of fiber optic connectors
- Difference between UPC and APC
- Products for fiber optic installers and service technicians
How is an optical cable constructed?
An optical cable is built from several basic layers that form a structure capable of transmitting data using light pulses. An optical cable consists of:
- Core This is the central element of the fiber, which plays a key role in data transmission using a light pulse. It is most often made of flexible glass fiber with a diameter similar to that of a human hair. The fiber from which the core is made is characterized by a high refractive index, which ensures total internal reflection of the light pulse inside the fiber core. The effect of total internal reflection allows the wave entering the core to maintain its parameters as it is reflected many times inside the core. This does not mean that the optical fiber does not generate any losses, but compared to copper cables they are significantly smaller.
- Cladding The next structural element of the fiber is the cladding. It is mainly made of glass with a lower refractive index than the core. Cladding provides protection for the core – it acts as a barrier for the transmitted light pulse. Thanks to it, data transmission is possible, because it directs the wave back into the core.
- Buffer coating The next element of the fiber is the buffer coating, i.e. a layer of material located on the outside surface of the cladding. It plays a key role by providing durability and resistance to environmental conditions and chemicals. The buffer coating is usually made from plastics such as polyethylene (PE), polypropylene (PP) or fluoropolymer materials such as FEP or PFA.
- Outer jacket The last element of the fiber is its outer jacket. Its task is to protect the entire structure against mechanical damage, moisture and UV radiation. Depending on the application of the fiber, various materials are used to make the outer jacket. The most popular of these are: polyvinyl chloride (PVC), polyethylene (PE) and thermoplastic polyurethane (TPU).
Appendix no. 1 – Drawing showing the construction of an optical fiber with its structural elements highlighted.
Classification of optical fibers by their structure
The choice of a suitable optical cable depends on application needs such as fiber bandwidth, distance, and installation and maintenance costs. With respect to modal types, optical fibers are divided into:
- Single-mode fibers (SMF) The core diameter in a single-mode fiber is about 8–10 μm (micrometers). Such cables are characterized by the transmission of a single light mode, which means that only one light pulse can travel through a given fiber. In the case of single-mode fiber, this pulse travels parallel to the axis of the fiber. Due to lower attenuation, their range is significantly greater than that of multimode fibers.
Appendix no. 2 – Drawing showing the construction of a single-mode fiber together with a representation of the direction of light pulse propagation inside the fiber.
Single-mode fibers in the TME catalog
- Multimode fibers (MMF) The core diameter in a multimode fiber is about 50 μm or 62.5 μm. Due to the larger core diameter, multiple light pulses can travel through the fiber at the same time. In a multimode fiber, the pulse propagates differently than in a single-mode fiber – the waves are reflected off the core walls at various angles.
Appendix no. 3 – Drawing showing the construction of a multimode fiber together with a representation of the direction of light pulse propagation inside the fiber.
Duplex-type fibers in the TME catalog
It is also worth mentioning that the cladding diameter is standardized and in both cases most often equals 125 μm.
Fiber categories – classification by transmission performance
With respect to transmission performance, categories have been assigned to optical fibers that describe their transmission speed. On this basis, we distinguish the following categories:
- OM transmission category (Optical Multimode)It applies to multimode fibers. Depending on the data transfer speed, it is characterized by various types of fiber:
- OM1 – the core diameter is 62.5 μm, while the total diameter is 125 μm (62.5/125 μm). The transmission capability for 10 Gb/s Ethernet is about 33 meters.OM1 multimode fibers
- OM2 – the core diameter is 50 μm, while the total diameter is 125 μm (50/125 μm). The transmission capability for 10 Gb/s Ethernet is about 83 meters.OM2 multimode fibers
- OM3 – the core diameter is 50 μm, while the total diameter is 125 μm (50/125 μm). Due to a laser-optimized core, the transmission capability for 10 Gb/s Ethernet increases to about 300 meters. OM3 multimode fibers
- OM4 – the core diameter is 50 μm, while the total diameter is 125 μm (50/125 μm). OM4 is an improved version of OM3 fiber. The transmission capability for 10 Gb/s Ethernet is about 400 meters. OM4 multimode fibers
- OM5 – the core diameter is 50 μm, while the total diameter is 125 μm (50/125 μm). The transmission capability for 10 Gb/s Ethernet is about 600 meters. OM5 multimode fibers
- OS transmission category (Polish: kategoria transmisyjna OS, English: Optical Single mode)It applies to single-mode fibers. Due to lower attenuation, their range is significantly greater than in the case of multimode fibers. It is characterized by the following fiber:
- OS2 – the core diameter is about 9 μm, while the total diameter is 125 μm (9/125 μm). The transmission capability for OS2 fiber is about 40 kilometers for 10 Gb/s Ethernet.OS2-category fibers
Most popular types of fiber optic connectors
Fiber optic connectors are key elements of fiber networks that allow two or more fibers to be joined. Permanent connectors are created by splicing or gluing fiber ends, which means that fibers joined in this way cannot be separated without damaging the connector. Detachable connectors are formed by bringing fiber ends together and properly positioning them using a mechanical housing. There are several types of fiber optic connectors differing in construction and the way fibers are joined. The most popular types of fiber optic connectors are:
- Fiber optic connector type LC (Lucent Channel) – these are some of the smallest connectors available. Due to their size, they are used in angled applications and those with space constraints.Fiber patchcords with LC connectors
- Fiber optic connector type SC – rectangular cross-section (Subscription Channel) – this is one of the most commonly used fiber optic connectors. It is characterized by a square shape and a push-pull latching system, which enables quick and easy mating and unmating. It is used in applications where high transmission performance is required. Fiber patchcords with SC connectors
- Fiber optic connector type FC – (Fiber Connector) – a connector designed for telecommunication applications where connection stability is required. This stability is achieved by using a threaded body.Fiber patchcords with FC connectors in the TME offering
What is the difference between UPC and APC?
With respect to the construction of the fiber connector end face (ferrule end), we can distinguish two polishing methods that are used depending on the connector’s application characteristics:
- UPC (Ultra Physical Contact) – a flat ferrule end with a convex profile, in order to minimize return loss. Typical return loss for UPC connectors is about −50 decibels. UPC connectors are usually blue.Patchcords with convex-profiled connectors
- APC (Angled Physical Contact) – a ferrule end polished at an 8° angle, which minimizes reflections returning to the source and improves signal quality. Typical return loss for APC connectors is about −60 decibels. APC connectors are usually green.Patchcords with angle-polished connectorsIn summary, APC connectors are preferred in applications where signal reflections must be minimized, while UPC connectors are used where low signal loss is important and reflections do not pose a problem.
Products related to optical fibers in the TME catalog
Optical cables and connectors are the foundation of fiber optic installations, but they are not sufficient to build a complete network. The TME catalog includes dozens of products intended for creating and maintaining fiber optic installations. These include, among others, fiber optic splicers, fiber network testers or fiber fault locators used by installers and service technicians. For such specialists, tools for crimping fiber optics and tools for stripping insulation will also prove indispensable. It is also worth mentioning optical splitters.
Transfer Multisort Elektronik (TME) is one of the world’s largest global distributors of electronic components, electrotechnical parts, workshop equipment, and industrial automation. The catalog includes over 1,500,000 products from 1,300 leading manufacturers. TME’s modern logistics centers in Łódź and Rzgów (Poland), with a combined area of over 40,000 m², ship nearly 6,000 packages daily to customers in more than 150 countries.
TME also invests in the development of knowledge and skills of young engineers and electronics enthusiasts through the TME Education project, and supports the tech community by organizing the TechMasterEvent series, promoting innovation and experience exchange.
