Significant progress has been made in optical fiber cable signal transmission distance

Optical fibre cable  is a communication cable consisting of two or more glass or plastic optical fiber cores located in a protective coating and covered by a plastic PVC outer sleeve. The signal transmission along the internal optical fiber generally uses infrared rays. In January 2013, Cuba carried out communications reforms, opening fiber optic cables and increasing foreign channels to attract attention.
The difference between PV wire and ordinary cable
First: There is a difference in material. Cables use metal materials (mostly copper, aluminum) as conductors; optical fibers use glass fibers as conductors.
Second: There is a difference in the transmission signal. The cable transmits electrical signals. Optical fiber transmits optical signals.
Third: There are differences in the scope of application. Cables are now mostly used for energy transmission and low-end data information transmission (such as telephone). Optical fiber is mostly used for data transmission.
Recently, researchers from University College London demonstrated a new method of processing optical fiber cable signals. Researchers claim that this method can double the error-free transmission distance of signals through submarine fiber optic cables. Because the new method does not need to strengthen the signal, it has the potential to cut the cost of long-distance optical fiber communications.

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The research was funded by the British Engineering and Physical Sciences Research Council, and the research leader Robert Maher said: “By eliminating the interaction between optical channels, we can double the error-free signal transmission distance from 3190 kilometers to 5890 kilometers. This is also the largest distance increase reported in the system architecture. “The challenge is to design a technology that can simultaneously capture a group of optical channels with a single receiver, called a super channel.” Maher added.
They use a 16QAM (quadrature amplitude modulation) super channel, which contains a set of frequencies. These frequencies can be encoded using amplitude, phase, and frequency to create a high-capacity optical signal. Utilizing a high-speed super receiver and a new signal processing technology developed by the team that can receive all channels without errors, the super channels can then be detected.

Now, researchers plan to test new methods of dense super channels that are commonly used in digital cable television (64QAM), cable modems (256QAM), and Ethernet connections (1024QAM).

Polina Bayve, Professor of Optical Communications and Networking, added: “We are very pleased to report this important discovery, which will improve fiber optic communications. Our method can greatly increase the efficiency of data transmission, almost double the signal transmission distance, which may greatly reduce the existing The cost of commercial systems. One of the biggest global challenges we face is how to maintain communications under the prosperous Internet demand. Overcoming the capacity limitations of fiber optic cables is the key to solving the problem.”

Different influencing factors, the degree of cross-linking of cross-linked cables is also different

Cross-linked cable is the abbreviation of cross-linked polyethylene insulated cable. It is composed of conductor, insulating material, internal and external semi-conductive material, sheath material, shielded copper tape, armored steel tape/steel wire, inner lining, isolation sleeve, filling material, etc. Part of the cable. Different components have their own usage requirements and characteristics. For example, XLPE insulated cables are the insulating medium material of XLPE, and the temperature resistance can reach 90°C. Therefore, the XLPE insulated cables cannot Compared with the advantages, it has simple structure, light weight, good heat resistance, strong load capacity, non-melting, chemical resistance, and high mechanical strength. It is mostly used in power transmission and distribution lines with power frequency AC voltage of 500KV and below.
In order to improve the temperature resistance of polyethylene, chemical or physical methods are usually used to make it into a body-shaped molecular structure. This is called cross-linking, which is the basic principle of cross-linking. So, do you know what is the degree of cross-linking of cross-linked cables? The following is an introduction to the factors that affect the degree of cross-linking of cross-linked cables for your reference.
1. Temperature
The temperature here not only refers to the working temperature of the cross-linked cable during cross-linking, but also includes the extrusion temperature. Specifically, it is:
(1) The cross-linking process is completed in the heating section of the vulcanized tube. Therefore, when other factors remain unchanged, the higher the temperature of the vulcanized tube, the higher the degree of cross-linking of the cross-linked cable. This is a certain point. Generally speaking, considering various factors, the temperature of the vulcanized tube for dry cross-linking should be around 290~310℃, otherwise the cross-linking degree of the cross-linked cable during cross-linking will be affected and will be greatly changed. Small, it is not a good thing for the use of cross-linked cables.
(2) Extrusion temperature. Because the cross-linked cable is processed, an extruder is required. If the cross-linking degree of the cross-linked cable is suitable, it is necessary to use a suitable extrusion temperature during the processing of the extruder, and the extrusion temperature may be related to the formula of the raw material, so this requires The material is fully plasticized without pre-crosslinking.
2. Linear speed during crosslinking
Obviously, the higher the line speed, the higher the production efficiency, but the degree of crosslinking will be lower. Therefore, when crosslinking, the line speed should be suitable. The line speed will be affected by factors such as rated voltage, cable specifications, cooling water temperature and water level, vulcanizing tube, etc. The larger the cable cross section, the greater the amount of glue required from the extruder, so the line speed cannot be too fast; The higher the temperature and the longer the pipeline, the faster the line speed; the higher the voltage, the thicker the insulation and the slower the crosslinking speed…
Well, the above is an introduction to the factors that affect the degree of cross-linking of cross-linked cables. I hope everyone can understand, and then cross-link correctly according to actual conditions and requirements.

How to protect cables from damage in cold winter

In winter, when laying and installing Aerial Bundle Cable (ABC) XLPE Insulated, many construction personnel will find that the wire and cable products with good quality usually have some problems, such as wire body hardening, insulation sheath falling off and damage. Many construction personnel think that the quality problems of wire and cable products have occurred, and the cable manufacturers insist that the products have been inspected before leaving the factory and are qualified Products often lead to misunderstanding between both sides. In fact, it is not the quality of the product itself, but the cold in winter.

The outer skin of PVC insulated AS / NZS 3560.1 power cable products is mostly ordinary plastic (PVC) or rubber. When they are in the environment below zero, they will become hard, and the whole wire and cable product line body will be hard and brittle, resulting in the skin may fall off and be damaged under slight external force. In winter, especially in the northern region, the outdoor temperature is often below zero, and the surface temperature may be lower. Therefore, if the wire and cable products are placed outdoors or directly on the ground, the product skin may fall off. So, how can we prevent the phenomenon of wire and cable sheath falling off in winter? Take the following measures from each stage.

1. When laying and installing the product: it is better to operate under the condition of relatively warm temperature in the middle and afternoon. If possible, the product can be “warmed up” in advance by using air heater and other equipment before use, so that the product can reach the best performance state. If buried, a protective layer can be laid in the cable trench, such as cloth and foam. If it is through the tube, the inside and outside of the pipe must be smooth in advance, so as not to scratch the wire. Special attention should be paid to the iron pipe. If the quality of the iron pipe is qualified, there may be a large number of sharp convex points in the poor quality iron pipe, which is likely to scratch the wire skin.

2, storage: it is best to store products in the room, and lay a layer of isolation layer on the surface of the storage, such as boards, bedding, foam and so on, to prevent the product from getting cold and damp.

3. When arriving at the destination or construction site, it is better for the product supplier to send personnel to supervise to prevent rough operation during unloading.

4. Ex factory transportation: when the products are loaded on the transport tools, they need to be kept warm and protected. For example, the use of closed means of transport to prevent direct exposure of products; put a soft cushion on the product, such as bedding or other softer foam, etc. when loading, gently handle lightly, do not load rough, at the same time avoid excessive bending of the product.

All in all, in winter, wires and cables will become very fragile, we need to “take care of”.

Three problems with cable insulation

It can be seen from the structure of the cross-linked polyethylene cable that there is a layer of outer semiconductor and copper shielding outside the main insulation layer of the cable. If this layer of outer semiconductor layer and copper shielding does not exist in the cable, then the core and core of the three-core cable Will an insulation breakdown occur during the period?

In the three-core cable terminal head, there must be a small section of the cable whose outer semiconductor and copper shielding layer have been stripped off, so is this small section of cable a weak link?
Can you overcome this problem by stripping less of the semiconductor and copper shielding layer (preserving the longer outer semiconductor and copper shielding layer as much as possible)? What is the disadvantage of keeping the longer outer semiconductor and copper shielding layer? The so-called “shielding” in the cable structure is essentially a measure to improve the electric field distribution. The cable conductor is formed by twisting multiple wires. An air gap is easily formed between it and the insulating layer. The surface of the conductor is not smooth, which will cause electric field concentration.Add a shielding layer of semi-conductive material on the surface of the conductor, which is equipotential with the shielded conductor and in good contact with the insulating layer, so as to avoid partial discharge between the conductor and the insulating layer. This layer of shielding is the inner shielding layer; Similarly, there may also be gaps at the contact between the insulating surface and the sheath, which is a factor causing partial discharge. Therefore, a shielding layer of semi-conductive material is added to the surface of the insulating layer. It has good contact with the shielded insulating layer and is in contact with the metal shield. The sheath is equipotential, so as to avoid partial discharge between the insulating layer and the sheath. This layer of shielding is the outer shielding layer; for extruded insulated cables without metal sheaths, in addition to the semi-conductive shielding layer, copper tape must be added Or the metal shielding layer wrapped with copper wire, the role of this metal shielding layer is to pass capacitive current during normal operation; when the system is short-circuited, it acts as a channel for short-circuit current and also plays a role in shielding the electric field.

It can be seen that if this outer semiconductor layer and copper shield do not exist in the ABC cable, the possibility of insulation breakdown between the core and the core of the three-core cable is very high. The main purpose of stripping off a small section of the shielding layer when making cable terminations or connectors is to ensure the creepage distance of the high voltage to the ground. The stress on the shielding fracture is very concentrated, which is a weak link! Appropriate measures must be taken for stress treatment. (Use stress cone or stress tube, etc.)

The length of the shielding layer is stripped to ensure the creepage distance; the basis is to enhance the creepage resistance of the insulating surface. Excessive stripping of the shielding layer will increase the difficulty of construction, and it is completely unnecessary to increase the cost of cable accessories.