Multicore fiber is a new type of fiber that has multiple independent cores in a common cladding area. Based on the concept of spatial division multiplexing, multi-core fibers can simultaneously transmit multiple optical signals in one fiber, greatly improving communication capacity and breaking through the current transmission capacity limit of ordinary single-mode optical fibers.
Due to the proximity of the fiber cores, there can be two functions:
One is a structure with large fiber core spacing, which means no optical coupling occurs. This type of optical fiber can increase the integration density per unit area of transmission lines. In optical communication, a ribbon cable with multiple fiber cores can be made, while in non communication fields, as an optical fiber transmission bundle, there are thousands of fiber cores made.
The second is to make the distance between the fiber cores closer, which can generate light wave coupling. Using this principle, dual fiber core sensors or optical circuit devices are being developed.
Multicore Fiber application
Laser, sensor or large-capacity core-division multiplexing transmission system
Multicore Fiber Features
- The number of cores can be customized, and each fiber core has low attenuation
- The spacing between each core is consistent
- Each core can be customized with the number of profiles and patterns
- In the case of small radius bending, optical fiber can well suppress bending loss
- Precise geometric parameters ensure low splicing loss and high splicing efficiency
- Each core MFD, cutoff wavelength, core spacing and fiber geometry can be customized
Multicore Fiber Types
There are several types of multicore fibers like 4 core fiber, 8 core fiber, 12 core fiber and 7 core fibers, etc
As shown in Figure 2, the end face structure of the multi-core optical fiber is displayed on the display screen of desktop endface microscope.
FAQ
What are the advantages of multicore fiber?
Multicore fiber can simultaneously transmit multiple optical signals in one fiber, greatly improving communication capacity and breaking through the current transmission capacity limit of ordinary single-mode optical fibers.
What is single core and multi core fiber?
Single core fiber is only 1 fiber core in common cladding layer, but multi core fiber has multiple fibers there. Let’s distinguish them from the structure.
The cross-section of an ordinary single-mode optical fiber is shown in Figure 2. From the inside to the outside are the core, cladding and coating layers. The core and cladding are made of glass materials with different refractive indexes. The coating layer is a layer of elastic paint cured with ultraviolet light to protect the fiber when the glass fiber is pulled out from the preform.
The diameter of the coating layer is 250um (after coloring) and the diameter of the cladding layer is 125um. Not many people pay attention to the core diameter of single-mode optical fiber, but what people pay attention to is the mode field diameter (For more information, please refer to article ”7 TYPES OF OPTICAL FIBER ”. The mode field diameter of single-mode fiber is approximately 9um (G.652, 1310nm).
Although the cladding diameter of single-mode fiber is almost the same as that of ordinary hair (the diameter of ordinary hair is about 60um~90um), it is still too large compared to the mode field diameter. So, why not put a few more fiber cores in the cladding, for example, put 7 fiber cores in the cladding, and it will look like this, see Figure 4
Figure 3 is still an optical fiber, but there are 7 cores, which is a 7-core optical fiber (Figure 1 shows a 19-core optical fiber). If each fiber core transmits one 100G, then this fiber can transmit seven 100G at the same time.
Are soft optical fibers and bundled optical fibers optical fibers or optical cables?
Soft optical fiber actually refers to a single-core fiber jumper, which refers to a single-core indoor optical cable with optical fiber movable connectors at both ends, as shown in Figure 5.
The structure of a single-core indoor optical cable is shown in Figure 5.
Bundle optical fiber refers to a multi-core indoor optical cable. It contains multiple ordinary single-core optical fibers inside, and then adds cable strength members and outer sheaths. They are not optical fibers, as shown in Figure 7.
So soft optical fiber and bundled optical fiber are not optical fibers, but cables.
What is a tight-buffered optical fiber?
Tight-buffered optical fibers are used in the indoor optical cables in Figures 5 and 6. The tight-buffered optical fiber is directly coated twice on the primary coated optical fiber, as shown in 8; the primary coated optical fiber is equivalent to the optical fiber shown in Figure 2 with the colored layer removed (outer diameter 245um). The coating layer and the covering layer are also called primary coating layer and secondary coating layer.
There are many outer diameters of tight-buffered optical fibers, the commonly used ones are 0.6mm and 0.9mm. Because tight-buffered optical fiber has good mechanical strength, it is usually used for pigtails on the equipment side, as shown in Figure 9 (in the figure, a tight-buffered optical fiber with a diameter of 0.9mm is connected to the fiber optic connectors).
The structural characteristics of tight-buffered optical fiber are still in line with that of optical fiber. Therefore, tight-buffered optical fiber is still an optical fiber, not a single-core optical cable.
