Optical fiber is made of silica glass through a complicated process. It is a highly transparent glass filament as thin as hair. The optical fiber transmit optical signal instead of electrical signal, so it is also called light-guide fiber.

As the transmission medium for optical communications, optical fiber has high efficiency, great capacity and strong anti-interference for long distance communications.

Fiber patch cord is used to make jumpers from equipment to fiber optic cabling network. There is a thicker protective layer outside the optical fiber.

It is generally used in the connection between the optical media transceiver and the terminal box, and some fields such as optical communication systems, optical fiber access networks, optical fiber data transmission, and local area networks.

Patch Cable Diameter

The 0.9, 2.0, and 3.0 of the fiber optic patch cord are used to distinguish the outer diameter of the optical cable. 0.9 means the outer diameter of the fiber optic cable is 0.9mm, 2.0 means the outer diameter of the fiber optic cable is 2mm. And 3.0 means the outer diameter of the fiber optic cable is 3mm.

Single Mode vs. Multimode

At the same time, there are single-mode fiber patch cord and multi-mode fiber patch cord. Normally, single mode is indicated by yellow fiber cable jacket, and multimode is indicated by orange fiber cable jacket. As for transmission distance, the fiber optic patch cord is the same as fiber optic cable, which single mode has longer transmission distance and multimode has shorter transmission distance.

Fiber Pigtail

The fiber patch cord has connector on both ends, how about fiber patch cable that only has connector on one end? This kind of fiber patch cable is called fiber pigtail.

The other end is a broken end of an fiber cable core, which needs to be connected to other fiber cable cores through fusion splicing. The fiber optic pigtail often appears in the fiber optic terminal box and it is used to connect the fiber optic cable to the fiber optic media transceiver.

Fiber Connector

Fiber optic connectors are also available in many types, and they cannot be used mutually. The SFP module is connected to the LC fiber optic connector, and the GBIC is connected to the SC fiber optic connector. Normal connectors are FC, SC, ST, MU, LC, MT, E2000, and MTRJ.

FC Connector

The external strengthening method is a metal sleeve, and the fastening method is a turnbuckle. Generally used on the ODF side (most used on the distribution frame)

SC Connector

the connector for connecting GBIC optical module or ordinary optical fiber transceiver. Its shell is rectangular, and the fastening method is plug-in bolt type, without rotation. (Most used on router switches)

ST Connector

commonly used in optical fiber distribution frame, the shell is round, and the fastening method is turnbuckle. (For 10Base-F connection, the connector is usually ST type. Often used in optical fiber distribution frames)

LC Connector

The connector for connecting SFP modules, which is made of easy-to-operate modular jack (RJ) latch mechanism. (Routers are commonly used)

The application of different fiber end face mainly depends on the type of adapter. Generally, FC is used in ODF frame, SC is used in equipment optical port, and ST is used in local area network and radio and television.

Fiber End Face

PC refers to physical contact, which is also close contact. According to the difference in return loss, connectors are divided into PC, SPC, UPC and APC.

PC, UPC, SPC

SPC refers to super physical contact, and UPC refers to ultra physical contact. The industrial standard of PC, SPC and UPC return loss are -35dB, -40dB and -50dB respectively (Return loss refers to the proportion of light reflected by the end face of the connector. The smaller the return loss, the better. Of course you can also say that the larger the return loss, the better, regardless of the negative sign in front).

Different connectors cannot be mixed in principle, but the fiber end faces of PC, SPC and UPC are all flat, and the difference lies in the quality of grinding. Therefore, the mixed connection of PC, SPC and UPC will not form a permanent physical damage to the connector.

APC

APC is completely different. Its end face is ground to an angle to reduce reflection. Its industry standard return loss is -60dB. The APC connector can only be connected with APC. Since the structure of APC is completely different from that of PC, if an optical adapter is used to connect these two connectors, the fiber end face of the connector will be damaged.

The only way to connect APC to PC is realized by the fiber optic patch cord that converts from PC to APC. In addition, it should be noted that the APC connector is usually green, and the human eye can see the tilt of the fiber end face.

APC connectors are usually green, and UPC/PC connectors are blue. Common connectors are FC/PC, SC/PC, SC/APC, and LC/PC.

Simplex vs. Duplex

A duplex fiber optic patch cable can be regarded as composed of two simplex fiber optic patch cable of the same specification.

When transmitting signals, the simplex fiber optic patch cord transmits two-way synchronously with one fiber core, and the duplex fiber optic patch cord send and receive signals in separate fiber core.

The advantage of the simplex fiber optic patch cord is it saves costs and application resources. And the advantage of duplex fiber optic patch cord is its high reliability.

Fiber Optic Adapter

With fiber connector on both end, fiber optic patch cord will connect the equipment or fiber optic cables by using optical adapter. Fiber optic adapters are used for the conversion of various fiber optic equipment and fiber optic connection methods.

With the wide application of fiber optic adapters in fiber optic connections, there are various fiber optic adapters. So they can have different interfaces to choose from to meet the installation requirements of different environments. Common types of adapters are: LC adapter, FC adapter, SC adapter, ST adapter, E2000 adapter, MTP / MPO adapter, etc.

The fiber optic cable lines used in FTTH network are generally divided into backbone fiber optic cable, distribution fiber optic cable, FTTH drop cable and the access fiber optic cable to user’s home, as shown in below diagram.

Generally speaking, the fewer fiber optic cable sections that a FTTH network passes through, the higher the security of the FTTH network. Then why is the FTTH network is divided into so many sections?

Data Center

If the FTTH network from the data center (or server room) to the user only passes through one optical cable segment (not counting fiber jumpers), that is, each user directly lays a fiber optic cable to the data center, as shown as below. What’s the problem? There are mainly two problems.

1. Number of incoming fiber optic cables is large, and the number of incoming fiber optic cable that a data center can hold is limited.
2. Long distance from data center to end user’s home is not convenient for installation, and costs are unimaginable.

Giving the above two aspects, the maximum number of users that can be accessed by such an office is only tens of households, and of course there is no application scenario.

Fiber Distribution Box

In order to solve the above problems, we have made two improvements, as shown in following.

1. The fiber optic cable comes out of the data center using a large fiber count one, and then split into multiple small fiber count optical cables with fiber splicing joint. Of course, if a fiber optic cable has too many points of splicing, it will affect the life and transmission performance of the optical cable.
2. Set up a fiber distribution box at a place where users are more concentrated, as the demarcation point between FTTH network and installation. When installing the access fiber network, they will only need to lay a small section of fiber optic cable from the fiber distribution box to the users.

Based on an data center with 10 fiber optic cable, and 6-12 fiber distribution boxes for each fiber cable, and 8 users in each fiber distribution box. It is estimated that the number of users served by a data center is 480 to 960.

At this time, the optical cable line from the data center to the user has become two fiber cable segments: data center – fiber distribution box, fiber distribution box – user. Since the connection of fiber optic cables is fixed at the splicing joint with small attenuation, the splice closure joint box is generally not considered as the starting point of the segmentation.

Compared with the first route map, the number of service users in the central data center has increased several times, but the capacity is still too small. In addition, the dynamic development of users requires flexible installation but not starting a new line from data center.

Fiber Splitting

From the comparison of the above two FTTH network, we can see that from the perspective of reducing the number of outgoing optical cables and facilitating installation, the capacity of the data ceter can be increased by adding branch points on the optical cables. The splicing points of optical cables are mainly achieved by fiber cabinet and splice closure.

One fiber optic cable can be splitter into multiple fiber optic cables through fiber cabinet optical splitting. The number of fiber optic cables that can be divided is mainly limited by the laying conditions of the fiber optic cables. The connection between the fiber optic cables is flexible, but it will increase the active connection loss and increase the difficulty of fiber core management.

The number of optical cables that can be splitted through the splice closure is small, normally no more than 6 (1 in 5 out). Generally, there will be remaining optical cables on both sides of the splice closure. If a splice closure has a large number of different fiber optic cables, the fiber cables will appear messy and unsightly, as shown in following picture. Therefore, in general, the number of fiber optic cables in the splice closure will be controlled within 4 (1 in 3 out).

After adding the fiber cabinet, the FTTH network structure from the data center to the user is shown as below. It is estimated that the number of users served by one fiber cabinet is 480 to 960 by using a fiber cabinet to connect 10 distribution fiber cables, 6 to 12 fiber distribution boxes for each distribution fiber cable, and 8 end users in each fiber distribution box.

So how many fiber cabinet can be set in a FTTH network? Based on the estimation of 10 backbone optical cables outgoing from one data center and 3 fiber cabinets for each backbone optical cable, 30 fiber cabinets can be set.

In this way, the capacity of a data center is approximately 14400-28800. With such a large capacity, FTTH network can basically meet the needs of many scenarios.

Distribution Fiber Cabinet

FTTH network will always be restricted by construction conditions. For example, if the optical fiber cable network is to cover a residential area, it is best to set up the fiber cabinet in the residential area. However, when the backbone optical cable construction of a bureau is carried out, they are allowed to carry out construction in most residential areas. And when the negotiations with a certain residential area for the construction conditions are finally settled, the backbone optical cable has been completed long ago.

The demand for network construction in residential areas, commercial buildings, and other cluster markets in cities is uncertain, and the construction of backbone optical cables must be completed within a certain period of time.

In order to solve this contradiction, during the construction of the backbone fiber optic cable, the fiber cabinet should be placed in a location close to the potential user group, where is convenient for fiber optic cable deployment, and with installation conditions.

When the construction conditions are available in residential areas, commercial buildings, and other cluster markets, install fiber cabinet at these locations, and lay optical fiber cables from the backbone fiber cabinet to distribution cabinet for communication.

In this way, the FTTH network from the data center to end users is divided into the trunk section, the distribution section, the lead-in section and the access section.

The setting of the fiber cabinet can further increase the number of users that the data center can cover. So how many distribution fiber cabinet can be carried under a backbone fiber cabinet? 5 to 10 are suitable. If you only have 2 to 3 fiber cabinets, it is more commercial to use splice closure instead.

Summary

At present, the FTTH network from the data center to end user is mainly a 4-segment structure we covered before. But we should also see that too many segments of the fiber optic cable will make the quality of the FTTH network worse and make the connection more complicated.

The separation of backbone fiber cabinet and distribution fiber cabinet is mainly to solve the problem of different construction timings of backbone optical cables and drop-in optical cables. In scenarios where the construction timing is not affected, such as when the coverage of a FTTH network belongs to the same town or the same residence, it doesn’t make much sense to set up the main fiber cabinet and the distribution cabinet separately.

Duct Fiber Optic Cable

The duct fiber optic cable is a multi loose tube stranded structure. Single mode optical fibre is put into the loose tube, and the loose tubes are filled with waterproof compound. The center of the duct fiber cable core is a metal steel wire reinforced core. For some fiber cable types, a layer of polyethylene (PE) needs to be squeezed outside the metal steel wire reinforced core.

All loose tubes (and filling rope) are twisted around the central reinforcing core to form a compact circular cable core, and the gaps in the cable core are filled with water blocking fillers.

Plastic-coated aluminum tape (APL) is longitudinally wrapped outside loose tubes and fillers. And then all materials are extruded into a cable with a polyethylene sheath. The structure and of this duct fiber optic cable is shown as below.

This duct fiber cable type has good waterproof performance and is suitable for occasions where pipe laying is the main method, and overhead laying can also be used.

Overhead Fiber Optic Cable

The core structure of overhead fiber optic cable is the same as that of duct fiber optic cable mentioned above. The difference is that its sheath is double-sided chrome-plated plastic coated steel tape (PSP) + polyethylene. The structure is shown in below. Compared with duct fiber optic cable, overhead fiber optic cable has better resistance to lateral pressure.

It is suitable for scenarios that require greater pressure on the side of the fiber optic cable. For example, in the section dominated by overhead laying, or for the access of home broadband, it can also be used for pipeline laying.

Direct Burial Fiber Optic Cable

Direct burial fiber optic cable can be understood as duct fiber optic cable being armored with double-sided chrome-plated plastic coated steel tape (PSP), and finally extruded into a cable with a polyethylene (PE) outer sheath. The structure of direct burial fiber cable is shown in below.

Direct burial fiber optic cable has good waterproof, side pressure resistance and tensile resistance, and is suitable for direct buried laying. Due to the high cost of direct burial optical cables and the inability to expand the capacity, the direct-buried method is no longer used for newly-built optical cable lines. Directly buried optical cables are mainly used for the maintenance of the original directly buried optical cable lines.

Flame Retardant Fiber Optic Cable

The structure of flame retardant fiber optic cable is the same as duct fiber optic cable. The difference is that the sheath of duct fiber optic cable is made of polyethylene material, and the sheath of flame retardant fiber optic cable is made of flame-retardant material.

This fiber cable type is mainly used for core network and the incoming sections of important convergence point. Generally, the length of each incoming optical cable shall not be less than 500m.

FTTH Drop Cable

FTTH drop cable is mainly used in the drop-in section of FTTH (Fiber to the home). It connects optical communications from the fiber distribution box to the user’s home ONT equipment. Based on its structure and shape, FTTH cable is divided into bow type drop cable (or butterfly drop cable), self-supporting butterfly drop cable, and prefabricated end.

Bow Type Drop Fiber Cable

In bow type drop fiber optic cable, optical fibre is placed in the center, which two parallel steel wires are placed on both sides as strengthening elements, and outside is extruded into cable with low-smoke halogen-free (LSZH) flame retardant sheath.

This fiber cable type has 1 or 2 cores in common use, the short and long axis dimensions of the sheath are 2mm and 3mm respectively. And the short-term allowable tensile force (minimum) is 200N. It should be laid along the wall or through pipes, rather than hanging in the air.

Self-Supporting Drop Fiber Cable

It is a non-metallic bow type drop fiber optic cable with a reinforced member (a steel wire or steel wire rope) attached to the outside.

The common fiber count of this fiber cable type is 1 or 2 cores, and the allowable tensile force (minimum) is 600N. It can be suspended in a short distance of less than 50m, which is suitable for introduction from outdoor to indoor.

Pre-terminated Drop Optical Cable

The pre-terminated drop cable is a fixed length bow type optical cable with SC connector prefabricated at both ends to reduce the workload of on-site termination during installation.

Hybrid Fiber Optic Cable

Hybrid fiber optic cable is the structure which optical fiber and insulated copper conductor are placed inside at the same time, so that one cable can solve the transmission of power and signal at the same time.

This composite hybrid fiber power cable is mainly used to connect BBU and RRU in DC remote supply system of distributed base station. And the voltage of DC remote supply system is usually DC 380V. There are usually two wires in the hybrid cable, and the cross-sectional area (mm2) of the copper wire is mainly related to the power and transmission distance of the remote communication equipment.

Hybrid fiber optic cable can be laid overhead or in pipeline. From the perspective of safety, hybrid cable line belongs to strong current line, and safety should be paid attention to in construction and maintenance.

Anti Rat Bite Fiber Cable

The structure of anti rat bite fiber cable is the same as that of directly buried optical cable, except that the corrugated steel tape of armor layer is made of stainless steel. This special optical fiber cable has high anti bite and anti-corrosion characteristics.

It is mainly used in the field farmland, forest and other areas where voles, squirrels and woodpeckers are active. It can be laid overhead, pipeline or directly buried.

Air Blown Fiber Cable

Air blown fiber, commonly known as air blown micro cable, adopts the structure of non-metallic reinforcement and no armor. It can be laid by laying micro pipe in the communication pipeline and then air blowing the micro cable in the micro pipe. The distance of one air blowing installation can reach 1km.

The outer diameter of air blown fiber cable is relatively thin, which can effectively use the existing pipe hole space. The number of commonly used air blown fiber is 36, 48, 72, 96 and 144 cores.

Air blown fiber cable shall be laid in microtubules, which is suitable for scenes with long section length where the number of optical cable cores does not decrease, such as trunk line and metropolitan backbone network. And the air blown fiber is not suitable for use in community broadband access network.

Underwater Fiber Optic Cable

Underwater fiber optic cable is a kind of optical cable that can be used underwater and underground. It is also called reinforced directly buried fiber optic cable. This special optical fiber cable can be understood as a cable formed by extruding the polyethylene outer sheath after being armored with one or two layer of round steel wire outside the sheath of a common duct fiber optic cable.

The underwater fiber cable has strong waterproof, tensile and lateral pressure resistance. According to the tensile strength, this special optical fiber cable can be used for

• direct buried laying in mountainous areas, hills, other areas with high tensile resistance requirements
• underwater laying with stable riverbed and beach and low velocity
• unstable riverbed and beach, flow velocity greater than 3m/s or main navigable rivers
• unstable riverbed and beach, serious scouring and super large rivers with river width of more than 500m

Ming Fiber Optic Cable

The mining fiber optic cable is also known as flame retardant fiber optic cable. It has the same structure as common direct burial fiber optic cable. The difference is that the outer sheath of regular direct buried optical cable is polyethylene material, and the outer sheath of the flame retardant optical cable is flame retardant material.

Mining fiber optic cable is a special optical fiber cable that must be used in the high standard requirements of high-speed railway and subway due to the restrictions of industrial specifications.

What is Mining Fiber Cable?

Mining optical cable is a special application of fiber optic cable in the field of optical communication. It is a communication optical cable that is professionally used in the mining industry. It is an optical cable used in mines such as coal mines, gold mines, and iron mines.

Mining optical cable not only inherits all the performance of fiber optic cable, but also adds many special performances due to the special requirements of the coal industry. Such as flame-retardant properties, anti-rodent properties (special mine environment).

What is The Mining Cable Standard?

Mines, iron mines and other mines, especially coal mines, are accident-prone areas. In order to ensure unblocked communication and reduce losses when accidents occur, the State Administration of Work Safety (National Coal Mine Safety Supervision Bureau) mandates all products used in coal mines. The safety certification also including the communication optical cable, which is mining product safety mark certification.

However, there are no corresponding standards for other mines such as gold mines and iron mines. The comprehensive performance of coal mine optical cables is the only standard currently used in mining. And it is also a relatively high implementation standard for the industry. Therefore, other mines are generally designed and produced in accordance with coal mine optical cables.

The mining fiber optic cable certified by the safety standard has practical scope of mines, tunnels, shafts, and roadways.

How Mining Fiber Cable Looks like?

The structure of the mine optical cable is divided into 2 types, central unitube type and multi loose tube (MLT) layer stranded type. Central unitube is for fiber count 2-12 cores, and MLT layer stranded type is for fiber count 2-144 cores.

Central Unitube Structure

For the central unitube type, there are optical fiber, fiber filling compound, loose tube, steel wire armor, steel tape, PE inner sheath, flame retardant outer sheath from inside out.

MLT Layer Stranded Structure

And MLT layer stranded type are made of central strength member (CSM) reinforcement, optical fiber, fiber filling compound, loose tubes, cable fillers, filling compound, steel tape, PE inner sheath, and outside flame retardant sheath.

Mining Fiber Cable Specifications

Mining Fiber Cable Types

According to the characteristics of the transmission medium in the optical cable, the optical fiber (glass or plastic fiber) is divided into single-mode optical fiber and multi-mode optical fiber. So the mining optical cable is divided into single-mode mining optical cable and multi-mode mining optical cable according to the optical fiber it used.

Single Mode

Single mode means that only one wavelength (frequency) is transmitted in the optical fiber. Optical fiber is slightly thicker than the hair, and it’s brittle, easy to break, and tough in tension, which is almost the opposite of the mechanical properties of human hair.

Due to the inconsistencies in the optical transmission performance caused by the other component characteristics of the medium, currently the main single-mode fiber used is B1.1, available wavelengths are 1310nm or 1550nm.

Multimode

Multimode means that multiple wavelengths (frequency) can be transmitted simultaneously in the optical fiber. Multimode optical fiber is generally using wavelengths 1310nm or 850nm

Optical Fiber Transmission Distance

Generally, the single-mode transmission can reach 120km without relay, and the multi-mode transmission can reach 2km. And the 10/100/1000M optical signal can generally reach 60-80km in the single-mode transmission without relay, multi-mode transmission is 500m with 50/ 125um, 200m with 62.5/125um. So multi-mode transmission is generally used for indoor or fiber patch cord, and single-mode is used for long-distance transmission in the field.

Optical Fibre

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