Author: Fiber-MART.COM

by http://www.fiber-mart.com

With the rapid development of data centers to ultra-high speed and large capacity, the market demand for high-speed optical transceiver modules is also increasing. Against this background, is there still market demand for low-speed optical transceiver modules? What does low-speed optical  transceiver module specifically refer to? Let us take a look below.

Low-speed optical module concept

According to the transmission rate, optical transceiver modules can be divided into 100M optical modules, Gigabit optical modules, 10G optical modules, 40G optical modules and 100G optical modules. We generally refer to optical transceiver modules with transmission rates of 1000M and below as low speed optical Module.

Classification of low-speed optical modules

Low-speed optical transceiver modules currently mainly include GBIC and SFP package types, they have certain differences in size and shape and their actual application.

GBIC optical transceiver module: The GBIC optical transceiver module is an optical module used in the early Gigabit Ethernet. It is mostly connected by sc interface. At present, only some of the earlier switch models of older models still have application requirements.

SFP optical transceiver module: The SFP optical transceiver module is an optimized version of the GBIC optical module. Its function is basically the same as that of the GBIC optical module, but its volume is much smaller. This type of optical transceiver module uses LC interface connection, which has the characteristics of compact structure and more Suitable for high-density wiring, it can greatly simplify the deployment of Gigabit Ethernet.

The working principle of low speed optical transceiver module

The low-speed optical transceiver module is composed of a transmitting part and a receiving part.

The function of the transmitting part is to modulate the electrical signal to the laser, so as to realize the electro-optical conversion. Specifically, the electrical signal with a certain code rate is processed by the internal driving chip to drive the semiconductor laser (LD) or the light emitting diode (LED) to emit the corresponding rate The modulated optical signal has an optical power automatic control circuit inside, which keeps the output optical signal power stable.

The function of the receiving part is that the detector receives the optical signal and realizes the photoelectric conversion. Specifically, an optical signal with a certain code rate is converted into an electrical signal by a light detection diode after being input into the module, and then an electrical signal with a corresponding code rate is output after passing through a preamplifier.

Application of low speed optical transceiver module

The low-speed optical transceiver supports many interface devices, including some other network devices such as switches and routers. In practical applications, SFP low-speed optical transceiver modules are more widely used than GBIC low-speed optical transceiver modules in the field of telecommunications and data communications.

However, there are still some network devices equipped with GBIC optical module interfaces, so the appropriate type of low-speed optical transceiver should be selected according to the interface type of the specific device.

by http://www.fiber-mart.com

Many people are confused about the hanging of aerial optical cables. In fact, there are two methods for aerial optical cables laying: one is “fixed-pulley traction method”, including “manual traction method” and “mechanical traction method”; the other is “cable tray moving and releasing method”. Next, we will take a detailed look at the concrete operation of the latest methods of aerial cable construction technology.

(1) Fixed-pulley traction method. When hanging the optical cable, the cable tray should be set first, and the big pulley for laying the optical cable shall be fixed on the pole at the up and down positions. A small pulley (guide pulley) shall be hung every 10-20 m on the suspension line in each pole, and the traction rope shall be put into the small pulley. Then, make the traction head, connect the traction rope with the optical cable, and prepare for laying.

① When applying manual traction method, please manually tighten the optical cable tray to gradually release the optical cable, and then one person shall be arranged on every two poles for auxiliary traction (if necessary, install guide pulley on the angle pole). Gradually tighten the traction rope at the traction end to slowly release the optical cable. In order to fully ensure the safety of optical fiber, three contact telephones shall be set at the cable laying end, cable receiving end and cable traction head of optical cable line, and always keep the contact unblocked. When the single tray optical cable is too long, it is generally placed in two times: after the first half of the tray is placed, put it on the ground with an “8” shape; and then the second half of the tray is placed in another direction.

② When mechanical traction is adopted, the main machine of mechanical traction shall be placed at the retrieving cable end, and the auxiliary traction machine shall be placed at the appropriate position of the cable laying end. Put the cable tray at the cable laying end, manually tighten the cable tray to gradually release the cable from the top, and apply machinery instead of manual traction to achieve the purpose of cable laying. When manufacturing the traction end, make sure that the traction force mainly acts on the reinforcement of the optical cable. With allowable traction force limit of optical cable, the length of optical cable laid in one time shall be determined according to the terrain conditions. In addition, the traction speed of optical cable traction machine shall be determined in advance. When the traction tension exceeds the standard figure, there shall be automatic cut-off or alarm device.

③ After laying optical cable, the length of optical cable for the joint and for each pole shall be reserved. Finally, hang the remaining cable with the wrapped end on the pole.

When laying the aerial optical cable of hanging type, the expansion bend can be properly made on the pole in the middle load area, heavy load area, overweight load area. It is generally required to be reserved on each pole. In the light load area, one reservation can be made every 3-5 poles; in the ice-free area, it is ok to make no reservation (but the optical cable cannot be pulled too tight, and pay attention to the natural sag).

The central part of the pole shall be protected by polyethylene bellows with a reserved length of 2m (generally not less than 1.5m). Both sides and binding parts shall be reserved, and shall not be tied up, so that it could expand freely when the temperature changes and the optical cable could thus be protected. When the optical cable passes through the cross-shaped suspension line or T-shaped suspension line, the protective pipe shall also be installed.

④ When the aerial optical cable is led upward, the aerial fiber optic cable installation method and requirements can refer to the following figure. The steel pipe (led upward to protect the steel pipe) is used to protect the lower part of the pole to prevent human injury; the upper suspension part shall be bound at the place 30cm away from the pole, and there should be an expansion bend (pay attention to the bending radius of the expansion bend and ensure the safety of optical cable with the condition of severe temperature change).

⑤ Generally, hooks are used for fixing and hanging aerial optical cables. The distance between optical cable hooks shall be 50cm, and the allowable deviation shall not exceed ± 3cm.

The buckle direction of the hook on the suspension line shall be the same, and the hook plate shall be complete without mechanical damage. The distance between the first hook on both sides of the pole and the clamp plate of suspension line shall be 25cm, and its allowable deviation shall not exceed ± 2cm.

(2) Cable tray moving and releasing method. Such hanging method is to set the optical cable tray on the truck (fix one end of the optical cable at the suspension line of the electric pole), manually push the optical cable tray, so that the optical cable is laid along the overhead line, while the optical cable is hung on the suspension line. After the laying work with one pole spacing, the optical cable can be fixed on the suspension line with next pole spacing. This method is simple, but the operation of truck is limited by conditions. In general, the following requirements shall be met.

It should be noted that the distance between the overhead line and the roadside is not more than 3m, and the suspension line should be located at the lowest layer of other lines on the overhead line. Unitek focuses on the R & D and sales of optical fiber and cable products. Optical fiber jumper, optical fiber adapter, MPO / MTP data center and other optical fiber products are all in line with international and domestic standards such as ICE, ROSH, and YD/T. We hope that you can firmly grasp the latest hanging methods above and apply them to actual wiring operation.

by http://www.fiber-mart.com

Central tube optical cable possesses loose tube structure of the central tube. Because its optical fiber is in the center of the cable, which has good bending characteristics and compact structure, it has become the main type after being introduced. Wuhan Institute of Post and Telecommunications Science, based on the characteristics of China’s vast territory and small optical fiber communication capacity at that time, has developed the first optical cable patent product with Chinese characteristics, that is, the central tube optical cable.

There are several forms of central tube structure. The first one has no steel belt armor, which is strengthened by parallel galvanized steel wire and has the problem of poor water penetration and bad low-temperature characteristics. Later, steel belt armor is added, and it is the first forming technology of optical cable steel strip longitudinal wrapping in China, adopting classification molding, steel belt flat belt butt joint, hot melt adhesive bonding process, which not only solves the problem of water penetration and high/low temperature, but also determines the rudimentary technical standard of steel strip. However, the optical cable is very difficult to peel. Finally, the technology of water blocking tape or oil paste filling is developed to further rationalize the structure. However, from the perspective of structural characteristics, if there are more than 12 cores are used, complex bundling technology is needed to distinguish optical fiber. Later, spraying ring technology is developed for OPGW. When multiple groups of optical fiber are placed in one tube, multiple fiber shelves are needed, so the utilization ratio of the equipment is limited, which is not conducive to large-scale production and not easy to be divided in project.

In 1991, Wuhan institute of post and telecommunications introduced NOKIA production line of loose tube, and introduced S-stranding cable from France. Then layer-stranding optical cable has been widely used. For S-stranding structure, the technology of synchronous back-twist of receiving and releasing line has been adopted. The cable pitch is stable, and the oil paste is filled and wrapped with polyester tape. The advantages are that the cable performance is stable, and the theoretical basis of cable surplus design today has been established. The disadvantages are complex equipment, low efficiency and high energy consumption. In 1995, SZ-stranding cabling equipment was developed, which greatly simplified the cabling equipment and improved the production efficiency. And the double-core shift winding, SZ reciprocating stranding process, ointment filling, longitudinal wrapping or wrapping tape were used to produce 12-unit tubes at most. The filling rope was developed as the filling unit, and two distinguishing methods of pilot color indication and full chromatography were designed.

The difference of cuff technique is that multiple optical fibers are arranged side by side. This technology was first used in skeleton ribbon cable in Japan, and the first one introduced into China was central tube ribbon cable. The key technology of optical fiber ribbon is paralleling fibers. The main index is the flatness control, and the colored optical fiber used in paralleling fibers is also different from the coloring process control of ordinary colored fiber. The other key is that the tidiness and tension of the winding line should match the cuff technique.

In cuff technique of ribbon fiber optic cable, ribbon fiber optic cable is usually stranded into tube with S or Z stranding structure, so the concept of the remaining length is different from that of the ordinary cuff. Because the cuff is thick, the wheel type traction is generally not used, while the track traction is mostly used. The key parameters to control the remaining length are: tension of ribbon releasing, pitch of pipe inlet, molds (multiple), water temperature and line receiving tension. Its theoretical calculation should specially include strain of each sideband and side fiber, and be connected with the actual test. In the initial stage, the duty ratio and pitch designed by each plant are relatively large. With the increase cost pressure, the technology began to be pushed towards the direction of small structure, which can best reflect the technology control ability of each plant in the ribbon fiber optic cable structure.

Skeleton ribbon fiber optic cable has its own characteristics in application because it has no ointment. In this period, only Chang Fei company introduced this technology, but it was not widely used. The main problems are: fail to produce 12-core ribbon; reduces the number of cores in one-time fusion; adopt S-stranded structure, which is not convenient for branching; complex equipment; high cost and low efficiency.

The emergence of butterfly optical cable is different from the previous design ideas. Its bare fiber is directly sheathed, which is designed based on the requirements of the last 100m of access network. There are pipeline and overhead, pipeline introduction and other laying forms. The process route is colored, sheathed or protected by aluminum tape sometimes. The tensile and temperature test of optical cable are different from those of ordinary optical cable. Burning characteristics and environmental safety factors are also considered.

The difficulty of this structure lies in the control of optical fiber loss, the control of optical cable structure size (need to cooperate with quick connector), the latest requirements of small surface friction coefficient for the construction of multiple optical cables in one pipe.

The traditional indoor optical cable is mainly jumper optical cable and short-distance indoor connection optical cable. With the development of FTTX, the types of optical cables in the building began to increase, including branch optical cables, wiring optical cables, etc.

These optical cables are all based on the tight cuff technology, and their materials are PE, AT, PU, PVC, LSZH, etc. They are quite different from the previous loose tube technology, and have various requirements for stripping.

by http://www.fiber-mart.com

The emergence of CWDM (coarse wavelength divisio

n multiplexing) technology allows operators to find a low-cost, high-performance transmission solution. Because of its low cost, low power consumption, small size, and other advantages, CWDM has been widely used in metro transport networks. Many domestic and foreign manufacturers have also begun to develop and launch products, and ITU is also accelerating its standardization process. CWDM technology improves fiber utilization and gives operators and users greater flexibility. This article will discuss the key technologies such as CWDM characteristics, wavelength selection, and fiber type, and make a detailed comparison between CWDM and DWDM. Finally, the application and development of CWDM are prospected.

Advantages of CWDM system metro transport networks

The biggest advantage of the CWDM system is its low cost, which is mainly manifested in several aspects of device, power consumption, and integration.

CWDM technology will greatly reduce the cost of construction and operation and maintenance, especially the cost of lasers and multiplexers/demultiplexers. For DWDM systems with awavelength interval of less than 50GHz, the laser needs to use a precise temperature control circuit to control the wavelength. And sometimes a wavelength locker is required to ensure the accuracy and stability of the wavelength. An optical multiplexer (filter type) requires hundreds of layers of multi-layer dielectric film devices. To prevent crosstalk between the same frequency and different frequencies, multiple filtering must be used. CWDM does not require complex technologies such as laser cooling, wavelength locking and precise coating, which greatly reduces equipment costs.

The DWDM system laser integrates a Peltier cooler. The temperature detection and control circuit uses a large amount of power and consumes about 4W per wavelength. The CWDMnon-refrigerated laser and its control circuit only require about 0.5W per wavelength. For multi-wavelength and high-speed DWDM systems, single-disk power consumption control is a difficult problem in system design. The low power consumption of the CWDM system using a non-refrigerated laser reduces power backup batteries and reduces costs.

The physical size of CWDM laser is much smaller than that of DFB laser. The size of DWDM optical transmitter is about 5 times that of CWDM optical transmitter. Due to the CWDM laser structure and simple control circuit, a single module can realize multi-channel optical transceiver. At present, commercial devices have achieved 4-channel transceiver integrated into a module with a size of only 16cm´9cm´1.65cm, which is equivalent to a DWDM system optical forwarding Size. The CWDM system does not use optical amplifiers, so it may be designed as a compact desktop or box-type device, which is very convenient for installation and maintenance.

The technology of CWDM

G.694.2 defines 18 nominal wavelengths of CWDM from 1270nm to 1610nm, and the wavelength interval is 20nm. This interval allows the simultaneous transmission of various wavelengths under the condition of using a non-refrigerated light source. The CWDM wavelength covers the O, E, S, C, L and other five bands of the single-mode fiber system.

The operating temperature (tube temperature) of non-refrigerating lasers usually ranges from 0°C to 70°C, and its thermal drift coefficient is about 0.08nm/°C. The nominal center wavelength value refers to the output wavelength of the laser at normal temperature, that is, 23°C. The filtering characteristics of passive devices (such as multiplexers) hardly change with temperature. It is generally believed that the nominal center wavelength of passive devices should be aligned with the output signal wavelength of the laser at 35°C, because 35°C is in the middle of the entire operating temperature range. In other words, the nominal center wavelength of the passive device should be l0 plus the wavelength drift value of the laser output from 23°C to 35°C, that is, l0 + 0.08nm/°C *(35°C -23°C) = l0+1nm. In order to solve the problem of wavelength difference caused by the difference between the nominal temperature of the laser wavelength and the actual operating temperature. The ITU shifts the G.694.2 wavelength up by 1 nm (1271 nm/1291 nm/…/1611 nm), so that the laser wavelength will just work at (1270 nm/1290 nm/…/1610 nm) in the actual environment.

In actual application, CWDM products mainly have two forms, 8-wavelength system and 16-wavelength system. The 8-wavelength system is a system with many applications. In theory,any one of the 18 wavelength choices given by ITU can be used as the operating wavelength. However, considering the type and loss characteristics of the optical fiber that has been laid, the 8 wavelength is generally selected at (1460-1620) nm, that is, the S+C+L band, avoiding the fiber water peak E band and the O band with greater loss. Additional requirements are required for optical fibers. The 16-wavelength system will impose requirements on the type of fiber, that is, a “full-wave” fiber with a flat loss must be used, and currently such fiber is rarely used. CWDM is mainly used in the access area lacking in optical fiber, and the capacity of 8 waves can mostly meet the system requirements.

According to the current laser manufacturing technology, the wavelength change of the non-refrigerating laser should be within +/- 6~7nm under working conditions and throughout its lifetime. Taking into account sufficient adjacent channel isolation and a certain guard band (generally the minimum channel spacing is about one-third), G.694.2 selects 20nm as the channel spacing of the CWDM system. In the CWDM system, the output wavelength of the uncooled laser at 0°C~70°C changes by about 6nm, plus the wavelength deviation of the laser manufacturing process is about±3nm, and the total wavelength change will not exceed±6nm. The passband of the optical filter and the wavelength spacing between adjacent channels must be wide enough to meet the requirement of no wavelength shift of the cooling laser.

The channel spacing of the CWDM system is usually 20 NM, and the filter passband width is about 13 NM. The laser center wavelength shift must be considered consistent with the filter passband width, and the laser output wavelength must be within the filter passband range.

by http://www.fiber-mart.com

Fiber optic adapters (also known as fiber optic flanges, mating sleeves and couplers), are fiber optic active components. Optical fiber adapters are the most useful optical passive devices in optical fiber communication systems. The fiber optic adapter plays the role of aligning the sleeve. In addition, the fiber optic coupler is usually equipped with metal or non-metal flanges to facilitate the installation and fixation of the connector.Both ends of the fiber adapter connect with fiber connectors of different interface types to achieve conversion between different interfaces such as FC, SC, ST, LC, MTRJ, MPO, and E2000. It is widely used in optical fiber distribution frames (ODF), optical fiber communication equipment, Instruments, etc..

Features of Fiber Optic Adapter

1. Passed 100% optical performance test, ceramic (zirconia) casing, processed with imported high-precision machine tool, high product finish, precise axis positioning, to ensure the coaxiality of the product and the accuracy factor of concentricity;

2. The unique design of the integrated internal structure, the structure is simpler, easier to use, easy to assemble, and improve efficiency;

3. Good stability performance, small insertion loss in continuous insertion test.

Classification of fiber optic adapters

There are various forms of fiber optic adapters. The adapters commonly used in EPON networks are APC adapters.

According to the different application scope and requirements of the fiber optic adapter, in order to fix it on various panels, the fiber optic adapter is also designed with a variety of fine fixing flanges. The fiber adapter can connect different types of fiber jumper interfaces. Duplex and multi cores adapters can increase the installation density. According to the difference in appearance structure and docking section, fiber adapters can be roughly divided into the following common models: FC, SC, ST, LC, FC-SC, FC-ST, ST-SC, in addition to some male to female hybird fiber optic adapter.

The external reinforcement method of FC fiber adapter is a metal body with screw buckle fastening method. FC fiber adapter adopts butt end with ceramic pins. This type of adapter is simple in structure, easy to operate, and easy to manufacture. However, the fiber end is more sensitive to fine dust, and Fresnel reflection is easy to occur. It is difficult to improve the return loss performance. Later, this type of adapter was improved, using a spherical pin (PC) with a mating end face, and the external structure was not changed, which made the insertion loss and return loss performance greatly improved.

The body of the SC fiber adapter is rectangular, and the structural dimensions of the pin and coupling sleeve used are exactly the same as the FC type. Among them, the interfaces of the adapter pins are mostly UPC or APC type grinding method. The tightening method of SC adapter is a plug-in pin bolt type, without rotating. The adapter is equipped with metal shrapnel, which is convenient for concealed installation. The SC adapter is inexpensive and easy to install and operate. The insertion loss fluctuation is small, and the compressive strength is high, which is suitable for high-density installation.

ST fiber optic adapter is a snap-on locking structure with key to ensure accurate alignment during connection and has strong tensile strength. Metal key positioning improves the repeatability and durability of the adapter. ST fiber adpter adopts precision ceramic or copper sleeves to ensure long-term stable mechanical properties and optical properties. Designed in rectangular structure, tapping riveting is easy to install.

The LC fiber adapter is made with a modular jack (RJ) latch mechanism that is easy to operate. LC fiber adapter adopts small size pins and sleeves which can increase the density of fiber connectors in the fiber distribution frame. And with adopts precision ceramic sleeve, long-term stable mechanical and optical performance can be ensured.

MT-RJ started with the MT adapter developed by NTT, with the same latch mechanism as the RJ-45 type LAN electrical adapter. The MT-RJ fiber adapter is aligned with the fiber through guide pins installed on both sides of the small sleeve. In order to facilitate connection with the optical transceiver, the fiber at the end of the adapter is arranged in a dual-core (interval 0.75MM) arrangement. MT-RJ fiber optic adapter is mainly used for next-generation high-density fiber optic connector of data transmission.

The important role of fiber optic adapters

Fiber optic adapters are components that play a key role in connecting optical fibers. There are multiple input ports and output ports of different models on fiber optical patch panel, no matter what type of optical fiber lines and equipment can be easily connected. The fiber optic adapter also has a function of establishing a signal branch. There are several outlets on the fiber optic patch panel, and each outlet can establish a branch line.

The application range of fiber optic adapters is very wide. First of all, it has an indispensable role in the fiber optic communication network. Our current network signals are all made of optical fiber, so the optical fiber has almost been drawn to thousands of households. Then there is the cable TV network. Some TV signals are also transmitted by optical fiber. In such a cable TV network, a signal source such as a voltage controlled oscillator is first used to generate electrical signals, which are then converted into optical signals by photoelectric elements. It can be transmitted by optical fiber, and the optical fiber adapter in this optical fiber TV signal network also has a very wide range of uses. In addition, optical fiber can also be used to build some local area networks for internal use by some units, and can also establish data connections between some electronic devices. These are also inseparable from optical fiber adapters. It can be seen that the role of fiber optic adapters in fiber optic communication networks is just as essential as the role of power connectors in circuits.

by http://www.fiber-mart.com

With the rapid development of the network, the 40G network has now become so popular, and the 100G network is also widely used. Nowadays, the traditional fiber optical LC connection can no longer meet the high speed and high density requirements of the data center. In this case, it becomes very important to obtain a higher transmission rate and find a suitable solution for high-density wiring. However, the emergence of MTP/MPO connection standards and MTP/MPO related products is indeed a good news for high-density cabling. It can replace 12 or 24 LC connectors at the same time. Therefore, it is the perfect solution for high-performance data transmission.

The MPO/MTP patch panel occupies a dominant position in the high-density wiring environment. As a high-density pre-terminated fiber optic equipment, it has the characteristics of flexible deployment and can not only provide conversion between MTP/MPO connectors and LC or SC connectors and help high-density networks to achieve rapid deployment, but also reduce the installation time and cost of optical networks. In addition, MTP/MPO distribution box is often used for MDA (main distribution area), IDC (Internet data center) or EDA (equipment distribution area) distribution area fiber backbone connection and fiber cabling management, MTP/MPO optic fiber distribution box can also be installed in a rack-mounted or wall-mounted cabinet to achieve capacity expansion.

The Characteristic Of MPO/MTP Patch Panel

1. It is usually installed in 19-inch racks and cabinets for centralized management of module boxes.

2. It can increase the number of ports through MPO/MTP modular design and provide high-density fiber connection.

3. MPO/MTP 1U fiber distribution box can be installed with MPO/MTP cassette modules, the MPO/MTP cassettes is installed with duplex LC adapters, the maximum number of fiber cores can be managed up to 96 cores.

4. MPO/MTP 2U fiber distribution box can be installed with 8 MPO/MTP pre-terminated cassettes, the MPO/MTP module box can be installed with duplex LC adapter to manage the maximum number of fiber cores up to 192 cores, and the MPO/MTP cassettes can be installed with simplex SC adapter to manage the maximum number of fiber cores up to 96 cores.

5. MPO/MTP 4U fiber distribution box can be install with 12 MPO/MTP pre-termination cassettes. The LC adapter can be installed in the PO/MTP cassettes to manage the maximum number of fiber cores up to 288 cores, and the simplex SC adapter in the PO/MTP cassettes can manage the maximum number of fiber cores up to 144 cores.

6. The design of optical fiber MPO/MTP patch panel includes cable manager and labeling strip.

7. It has the advantages of convenient installation and cable management.

8. Compare with the traditional fiber optical patch panel, the density of MPO/MTP fiber optic box is more than four times, which greatly saves the space of the cabinet, improves the utilization rate of the cabinet, and creates value for the construction of the data center.

The Application of MPO/MTP Pre-terminated Patch Panel

The MPO/MTP pre-terminated fiber optic patch panel is the end point of a backbone optical cable, which is equivalent to a device that breakout an optical cable into a single optical fiber. Its function is to provide MPO/MTP trunk jumpers and MPO/MTP adapter pre-connected, MPO/MTP to LC/SC jumper and LC/SC adapter connection. It provides mechanical protection and environmental protection for optical fibers and their components, and allows appropriate inspections to maintain high standards of optical fiber management.

fiber-mart.com provides customized high-quality optical fiber Patch Panels, MPO/MTP Distribution box and other fiber optical products according to customer needs. With more than 10 yeas developement, UniteFiber supplies high-density optical fiber products, PLC optical splitters, WDM wavelength division multiplexers, optical switches and other products, which are widely used in FTTx, telecommunications, 5G networks, data centers and other fields.