How does FBG (Fiber Bragg Grating) Optical Reflector work?

FBG fiber optic reflector, also known as Fiber Bragg Grating Filter, is usually installed on the front end of the ONU. Combined with OTDR equipment, it can realize the point-to-point (PTP) or point-to-multipoint (PTMP) network monitoring of optical link, which can reflect the network abnormality quickly and accurately.

What is FBG? FBG is Fiber Bragg Grating. A fiber grating is a type of diffraction grating. Fiber Bragg Gratings (FBG) is a simple and low-cost way to build a grating into a specific wavelength range of fiber. When broad-spectrum light is incident on the fiber with built-in grating, the wavelength matching the grating will be reflected back to the input end, and the rest of the light will be passed through to the other end. Fiber gratings have the characteristics of small size, good wavelength selectivity, good compatibility, etc. The manufacturing process for fiber gratings is mature, with good practicality and low cost, they are widely used in the field of communication and sensing and is also ideal important device in optical network.

The FBG optical reflector utilizes the wavelength selectivity of the fiber grating, and the fiber grating is embedded in the adapter. It can be conveniently installed on the front end of an optical network (ONU), and it can quickly and accurately implement optical network fault detection with the help of an optical time domain reflector (OTDR). Due to the excellent wavelength selection characteristics of fiber gratings, anti-electromagnetic interference, the center wavelength drift is small with the change of external temperature, and when the optical network coverage and depth continue to increase, the entire optical network fault point can be detected quickly and accurately.

With the application of optical splitters in passive optical network (PON) networks, the complexity of the ODN network deployment environment has been increased. The splitters at the end of the FTTx will split the trunk optical signals and increase the difficulty to identify attenuation events on ODN branch fibers. The application of fiber grating reflector is a wavelength selective reflector based on this environment, which aims to improve the fast and accurate detection of optical link failure events by OTDR.

The fiber optic reflector is usually installed on the ONU side. The OTDR detects the intensity of the optical signal reflected by this reflector and compares the return loss between the normal line and the failed link to determine whether the optical fiber in the link is damaged or not. The normal PON system working wavelength does not meet the reflector conditions then will pass through the reflector with a small attenuation. While the reflector achieves the monitoring function, but without disturbing the transmit. 1650nm fiber grating reflector, the grating reflection wavelength is 1645 ~ 1650nm. The optical signal in this Bragg wavelength range will return along the input path, and all other wavelengths of light (1260 ~ 1625nm) can pass through. If the input optical signal segment can detect the fiber grating reflection peaks in this band, it can be judged that the transmission path is normal. Otherwise, it is abnormal.

End-to-end OTDR measurement from the OLT to the ONT is usually difficult because the splitter brings high losses and complex networks. The application of fiber optic reflector is a cost-effective solution to help OTDR detection, and it is the best way to implement real-time end-to-end (OLT to ONT) monitoring of optical networks in FTTx networks.

HYC’s self-developed FBG fiber optic reflector has the advantages of low insertion loss, high reflectivity, and easy installation. It is widely used in PON networks, OTDR testing, central computer room testing, FTTX and other fields. It can be customized as special pigtail or adapter type, and the connector interface is LC, SC APC / PC.

HYC Innovative Product, 1×48 MEMS Optical Switch

The upcoming 5G application promotes the upgrade of the all-optical network (AON). As a key part of the all-optical network, the ROADM market is expected to usher in rapid growth, especially in metropolitan area networks.

MEMS optical switch is one of the core devices in ROADM. Optical switch is a kind of optical path controlling device, with the ability to control and switch the optical path. MEMS fiber optic switches are based on micro-electro-mechanical system (MEMS) technology, which achieved low insertion loss and highly repeatability by rotating the mirror of MEMS chip.

Fiber Optic Patch Cable PC, APC or UPC

To make better contact between the ends of the two fibers, the ferrule end faces of the fiber optic patch cable is usually polishing into different structures. Standard polishing methods are PC, APC, and UPC. PC/APC/UPC represents the front end structure of the ceramic ferrule.

Different fiber end face finishes
PC (Physical Contact).The two end faces are polished to be slightly curved or microspherical, and the fiber core is at the highest point of the bending. This eliminates the air gap and forces the fibers into physical contact.

UPC (Ultra Physical Contact) is based on the PC to optimize the end face polishing and surface finish, the end face looks more dome-shaped. The end face of the UPC connector is not entirely flat, and there is a slight arc to achieve more accurate connecting.

APC (Angled Physical Contact). The end face of APC is usually polishing into an 8-degree angle. The 8° angled bevel makes the fiber end face tighter and reflects light through its beveled angle to the cladding instead of returning directly to the source, providing better connection performance.

Different physical appearance
The APC fiber optic connector is usually green. UPC/PC connectors are easily identified by their blue color on the connector boot.

Insertion loss and return loss
Different polishing styles determines the quality of optical fiber, which results in different performances regarding the connector's insertion loss and return loss. Insertion loss refers to the signal loss caused by the connector or cable. In general, the typical insertion loss of PC, UPC, and APC connectors should be less than 0.3dB. Compared with APC connectors, UPC connectors are usually easier to achieve low insertion loss due to the smaller air gap. Insertion loss can also be caused by a tiny particle of dust trapped between the connector end-faces. A single dry debris particle could even damage the fibers and ferrules.

Return loss, also known as reflection loss, is a parameter representing the signal reflection performance. Usually expressed in negative dB value, the higher the value of the setting, the better. The end faces of APC connectors are beveled, so the return loss of APC connectors is usually better than UPC connectors. In general, the return loss of the PC fiber cable is -40dB. UPC return loss is higher relative to PC, generally at -55dB (or even higher). APC industry-standard return loss is -65dB. With the UPC connector, any reflected light is directly reflected back to the light source. The beveled end face of the APC connector allows the reflected light at an angle into the cladding instead of reflecting it directly to the light sources. This is the main factor that causes the return loss to differ.

Applications
PC is the most common grinding method for optical fiber connectors, which is widely used in telecommunication operator equipment. UPC is commonly used in Ethernet network equipment (such as ODF fiber distribution frames, media converters and fiber switches, etc.), digital, cable television and telephone systems. APC is generally used in optical radio frequency applications such as CATV, and also in passive optical applications, such as PON network structures or passive optical local area networks.

Connector connections need to be in the same end face structure; for example, APC and UPC cannot be mated together , because doing so will resulting in poor connector performance. However, the end faces of PC and UPC fibers are flat, and the difference is in the quality of grinding. Therefore, the mixed connection of PC and UPC will not cause permanent physical damage to the connector.

HYC has 19 years of experience in research and development of fiber optic component manufacturer , supplying all kinds of fiber connectors and fiber patch cords for various specifications.

Introducing MPO/MTP Fiber Patch Cord，Optical Fiber Connector

With the increasing demand for high-speed, high-capacity optical communication systems, MTP/MPO fiber optic connectors and fiber optic patch cord are ideal solutions for high-density cabling in data centers due to their cores, small size, and high transmission rate.

The MPO fiber patch cord is a combination of an MPO connector and a fiber optic cable. The MPO connector type is distinguished by several factors according to IEC 61754-7: Array Number, Male-Female, Polarity, Polishing type (PC or APC).

MPO fiber optic connector types
Currently, the factory termination assembly of the MPO connector can accommodate 6 to 144 fibers, among which 12 and 24-core MPO connectors are the most common types. According to IEC-61754-7 and EIA/TIA-604-5 (FOCIS 5) specifications, 12-core fibers are usually arranged in a row, which can consist of one or more columns of fibers in the same MPO connector. There are 12-core fibers MPO connectors and 24-core fibers MPO connector. 40G MPO-MPO fiber jumper generally adopts 12-core MPO multi-mode ferrule; 100G MPO-MPO fiber jumper, generally uses 24-core MPO ferrule. There are also 16 single-row fiber array types on the market that can be divided into multiple columns to form 32 cores or more. The 16/32-core MPO fiber optic connector will be the best solution for low-latency, the ultra-high-speed transmission of next-generation 400G networks.

Male and Female Connectors
MPO connectors contain several parts such as boot, coupling/housing assembly, ferrule, guide pins, and so on. Because of difference pins types, the MPO connector can be either male or female. The male connector has metal guide pins to ensure fiber alignment when mating while the female connector has no pins. These pins make sure that the connector fronts are precisely aligned on contact and that the fibers’ end-faces aren’t offset.

What is MTP?
MTP is “Multi-fiber Termination Push-on”, which was developed by US Conec and improved attenuation and reflection on the standard MPO connector with higher overall performance. Externally, there is little discernible difference between the MPO and MTP connectors. They are completely compatible.

MPO/MTP fiber connectors and fiber patch cords provide a simple and easy-to-manage fiber-optic cabling solution for FTTH and data centers that require high-density integrated fiber-optic system. It is likely to be a hot-demand product for future 5G data center construction.

HYC has 19 years of experience in research and development of passive basic components for optical communications, supplying MPO/MTP fiber connectors and fiber patch cords of various specifications.

What are the features of LC Uniboot compared to traditional LC fiber connectors?

The traditional LC duplex fiber optic connector is generally composed of two LC simplex connector through a clip, with a single fiber inside each connector. The LC Uniboot connector is a modified LC duplex connector. The two fibers are simultaneously placed in a 2.4mm or 3.0mm jacket to achieve a single-tube dual-core function, which significantly reduces cabling space requirements. So what is the difference between an LC uniboot connector and a traditional LC fiber connector?

Compact design for high-density applications
LC Uniboot optical connector adopts single-tube dual-core, half-surround tab end to reduce the number of fibers. Compared to traditional LC duplex jumpers, the uniboot connector effectively reduces installation volume by 50%, including improved cable management, airflow, and cabling.

Easy polarity revisable
What is fiber polarity? The polarity of optical fiber is the direction of optical signal propagation in the optical fiber. Normally, there are a transmitting signal terminal (Tx) and a receiving signal terminal (Rx). The Uniboot connector is an innovative design that allows the fiber polarity to be switched without the need for special tools.

A push-pull tab design
HYC’s LC Uniboot connector is an exclusive patent design with a push-pull tab, which ensures easier release from the high-density environment. The fiber optic connector with a push-pull tab is easy to insert or remove even in high-density environments. A half-surround tab end avoids the cable ganged each other.

The innovative LC uniboot optical fiber connector, with its unique structure and compact design, performs better than conventional LC duplex connectors in a high-density cabling environment, making it an ideal choice for data centers and FTTx.

The Features of Slide Out Drawer Optical Fiber Distribution Box

As the number of users increases, optical fiber cabling becomes more and more complicated. Optical Fiber Distribution Box (ODB) is an important equipment in the optical transmission system. It is usually placed in an optical communication room or rack to manage fiber terminals and implement cabling functions. It is widely used in optic communication room, fiber optic connecting devices to manage fiber terminals and it can function as the protector of optical cable termination and line transmission.

In general, there are three types of fiber optic distribution boxes: rack mount type ODF, cabinet mount type ODF, and wall mount type ODF. Rackmounts are usually 19 inches and come in units of 1U, 2U, 3U, or 4U. U is Unit, which generally refers to the height of the panel device. To be precise, 1U is equal to a rack height of 44.45 mm (1.75 inches) and a 2U mounting height is 2 x 44.45 = 88.88, which is 3.5 inches high. The height of the 3U is 3 x 44.45 = 133.35mm, which is 5.25 inches. The standard was established by the Electronic Industries Association (EIA). The main difference between the IU/2U/4U fiber distribution box is the height and the number of fiber cores that can be supported.

Rack mount enclosures are the most commonly used fiber-optic enclosures for the telecommunications industry. They come in different sizes and types with customizable panels and trays. Rackmount fiber optic enclosures are divided into different installation methods: drawer type, swing-out type and cover removable type. Drawer and swing-out types of fiber enclosures are more convenient to use but they are also more expensive. The cover removable type fiber enclosure is cheaper, but not as convenient. The cover removable type rack mount enclosures are the most commonly used fiber-optic enclosures for the telecommunications industry. What are the characteristics of the drawer type fiber enclosure?

Split tray design, easy to operate
The drawer-type fiber enclosure uses a split tray, and the module box can be pushed and pulled independently when they are stacked and installed. The mounting area is equipped with a separate pull button lock to prevent slipping. The tray has a sliding and locking function, which can be directly pulled out like a drawer when in use, and can be wired after being locked out, which is very convenient.

Compact structure, super density cabling, effective space-saving
The compact design allows for high fiber density and more port number to increase cabling density and maximize cabinet space savings. This HYC’s high-density unique design patch panel, with maximum LC connecting & cabling, adopt the high-strength environmental lightweight material and superior surface treatment technique, which make the panel achieved complete function and various flexible cabling solution. Each cassette module is designed with 24 fibers, 6pcs cassettes can be put in 1U, which equipped up to 144 core LC interface or 72 core SC interface. 2U can accommodate 12 cassettes, with 288 core LC interface or 144 core SC interface; 4U can be equipped with up to 576 core LC interface or 288 core SC interface.

Flexible design, efficient cable management
There is an independent cable management frame at the back of the enclosure, which can easily manage the cable and ensure the air circulation in the space. HYC’s fiber optic panel is designed with good cabling management. The independent cassette at the front side is for smart cable management. Multi-layer cassette for easy separated operation. The independent cable management frame at the backside is to fix the trunk cable. The redundant trunk cable ensures the cassette move properly.

The drawer-type fiber distribution box is flexible in configuration, easy to install, easy to maintain and manage. It is widely used in patch cord connection, fiber fusion, fiber storage, and high-density MTP cabling management.

HYC can design a fiber-optic enclosure that meets all your business needs. HYC Patch Panel Enclosures are available in 1U, 2U, and 4U heights and may be configured to offer dozens of high-performance networking solutions.

HYC Co., Ltd（HYC）is a national Hi-tech optoelectronics company engaged in R&D, manufacture, and marketing of fiber optical products. Providing professional products and services for fiber connectivity, WDM, PLC splitter, and high-density datacom cabling. HYC products and solutions widely applied in 4G/5G, Data Center and Cloud Computing industry, etc.

A comprehensive understanding of fiber optic connectors

Optical fiber connectors are used most often to transmit light by connecting two optical fibers instead of splicing. It is a flexible device that widely used in fiber-optic communications systems. Optical fiber connectors ensure precisely connections between the two ends of the fibers so that the optical energy output from the transmitting fiber can be coupled to the receiving fiber to the maximum extent. Better connectors will have little impact on the system due to its involvement. Since the outer diameter of the optical fiber is the only 125um, and the light passing core is smaller. The cores of single-mode fiber are only 9um, and the multi-mode optical fiber has 50um and 62.5um. So it is important to ensure the properly aligned.

Main component: Ferrule
One of the most important main components of fiber optic connector is ferrule. The quality of the ferrule directly affects the precision connections of the two fibers. Ferrule is usually made of different materials such as ceramic, metal or plastic. Most of the ferrules used in optical connectors are made of ceramic material (zirconia) due to its hardened characteristics, such as good thermal stability, high hardness, high melting point, wear-resistance, and high processing precision. The inner diameter of the ceramic sleeve is slightly smaller than the outer diameter of the ferrule, and the slitted sleeve tightens the two ferrules for precise alignment.

In order to make the end faces of the two fibers better contact, the ends of the ferrules are usually poshing into different structures. PC, UPC, and APC are the polish styles of ferrules inside the fiber optic connectors. PC is Physical Contact. The two end faces are polished to be slightly curved or microspherical, and the fiber core is at the highest point of the bending. This eliminates the air gap and forces the fibers into physical contact. APC is Angled Physical Contact. The end face of APC is usually ground into an 8-degree angle. The 8° angled bevel makes the fiber end face tighter and reflects light through its beveled angle to the cladding instead of returning directly to the source, providing better connection performance. UPC (Ultra Physical Contact) is based on the PC to optimize the end face polishing and surface finish, the end face looks more dome-shaped. Connector connections need to be in the same end face structure, for example, APC and UPC cannot be combined, resulting in poor connector performance.

Basic parameters: insertion loss, return loss
Due to the different ferrule end faces, the performance of the connector loss is also different. The optical performance of fiber optic connectors is primarily measured by two basic parameters: insertion loss and return loss. So what is the insertion loss? Insertion Loss (“IL”) is the loss of optical power caused by the connection. It is mainly used to measure the optical loss between two fixed points in optical fiber, which is usually caused by the transverse deviation between two optical fibers, the longitudinal gap in optical fiber joints, the end mass, etc. The unit is expressed in decibels (dB). Lower the insertion loss, better the performance. The general requirement should be no more than 0.5dB.

Return Loss (“RL”) refers to the parameter of signal reflection performance. It describes the power loss of optical signal return/reflection. The value is usually expressed in decibels (dB). The larger, the better. The typical RL value of APC connector is about -60db, and that of PC connector is about -30db.

Except for the two optical performance parameters of insertion loss and return loss, there are also other parameters should be considered including the interchangeability, repeatability, tensile strength and operating temperature of the fiber optic connector.

Fiber optic connector types
There are various fiber connector types in the market, such as LC, SC, FC, ST, MU, MT, MPO/MTP and so on.

LC connector
The LC optical connector is made with an easy-to-use modular jack (RJ) latch mechanism. The size of the pins and sleeves used in the LC connector is 1.25 mm, which is the half-size of SC, FC, etc..

SC connector
SC fiber optic connector (‘Subscriber Connector’ or ‘Standard Connector’) is a snap-on standard square connector, which features a push-pull coupling mechanism, and does not need to be rotated. This type of connector is usually made of engineering plastics, which are inexpensive and easy to insert and remove.

FC connector
FC fiber connector (Ferrule Connector) and the SC connector are the same sizes, except that the FC is made of a metal sleeve and the fastening method is a turnbuckle. It has the advantages of simple structure, convenient operation, easy manufacture, and durability, and can be used in a high vibration environment.

ST connector
The ST fiber optic connector (Straight Tip) has a rounded outer that made by a 2.5mm ring-shaped plastic or metal. The bayonet-style keyed coupling mechanism, which is commonly used in fiber distribution frames.

MTP/MPO connector
The MTP/MPO fiber optic connector is a special type of multi-fiber connector. The structure of the MPO connector is complex, connecting 12 or 24 fibers in a rectangular fiber ferrule.

In addition to the above, the connector types include MU connectors, MT connectors, MTRJ connectors, E2000 connectors, etc. Due to low cost-benefit, SC connector is probably the most commonly used fiber optic connector. LC fiber optic connectors are also a commonly used fiber optic connector, especially for connection to SFP and SFP+ fiber optic transceivers. FC connector is mostly used in single-mode and is relatively rare in multimode fiber. Complex designs and metal housing makes it more expensive. ST fiber optic connectors are typically used in long and short-range applications such as campus and architectural multimode fiber applications, enterprise network environments, and military applications.

Choosing the appropriate connector for a fiber network depends on things such as network design and function. HYC(HYC Co., Ltd)offers a variety of fiber optic connectors of various specifications and types, including SC, FC, LC, ST, MPO, MTP and so on.