# What Is Singlemode and Multimode Optical Fiber?

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Light is an electromagnetic wave (visible light frequencies in the order of 10 ^ 14), singlemode fiber and multi-mode fiber optics are needed to explain fluctuations. The basic formula is the electromagnetic theory of Maxwell’s equations, the boundary conditions of Fiber Optic Cables (size, refractive index, wavelength and other parameters) into Maxwell’s equations.

The solution obtained contains numerous real and imaginary part, representing the spatial distribution of the electromagnetic field and the transmission, each solution can be called a mode, the real part can be interpreted as conductive portion for satisfied the total reflection conditions, it can be called the conduction mode. the imaginary part is rapid loss in the transmission swap, known as radiation modes. The solution with the fiber size, fiber core and cladding refractive index, the wavelength dependence of the incident light. When the fiber core size decreases, the mold can be found rapidly reduced conduction, in particular core size and wavelength may be compared, the conductivity is reduced to the mode field distribution is also a space appears discontinuous, showing the geometrical optics can not be explained. “quantum properties. “When reducing the fiber core size to a certain number, the only one possible conduction mode, this time, the optical fiber for this incident became a single-mode fiber.

Single Mode Fiber Patch Cable is relative, when the wavelength of the incident light is reduced, there will be a new conduction mode, this is relatively light, Fiber has become multimode fiber. So there is a cutoff wavelength of a single-mode fiber that is higher than this wavelength, which is the single-mode fiber. G 652 common singlemode fiber cutoff wavelength less than 1260nm.

Multimode Fiber Optic Cable can be understood as approximately the incident light along many different paths in the optical fiber transmission angles. Clearly different from the other end along the length of the different paths, because the length of the transmission time difference generated by different known mode dispersion (i.e. different paths in different modes).

Single mode optical fiber can transmit along a path (ie, only one mode), there is no mode dispersion. But with different refractive indices in different wavelengths of light in the same material, resulting in different transmission rate, so if the same beam of light contains different frequencies, the other end to the optical fiber transmission time is different, this causes the transmission time difference is called Single-mode dispersion or material dispersion or wavelength dispersive. Not the kind of light source is entirely monochromatic, the wavelength dispersion is widespread. We usually use several sources of communication, the wavelength dispersion smaller than the mode dispersion.

Common single-mode fiber (G 652) is about 8-10um core diameter, the related proudcts from Fiberstore, it’s Duplex 9/125 sc to sc fiber patch cord.  The picture is follow:

Sc to Sc Fiber Patch Cord is for high bandwidth and transmission rates over longer distances. This SC fiber patch cable  is specifically designed for gigabit ethernet applications. The patented injection molding process provides each connection greater durability in resisting pulls, strains and impacts from cabling installs.

Common multimode fiber core diameter, there are two types, 50um and 62.5um. The related products from Fiberstore, it’s Duplex OM1 Multimode 62.5/125 Lc-Sc Fiber Patch Cable. The picture is follow:

# The Development and Benefits of Multi core Singlemode Fiber

1. The development of multi core single mode fiber

2. Design of multi core singlemode fiber

To meet the needs of FTTH systems. The design of multi-core fiber should meet the following key requirements: 1.31 um and 1.55um wavelength dual-window work; Crosstalk between each core is greater than -35 dB: precise geometry; Easy identification of each core and ordinary Single mode Fiber Optic Cable. Further, since the optical fiber length shorter in FTTH network (≤ l0 km), so the requirements for dispersion and attenuation of the fiber is relatively relaxed, there are strict requirements on bending and microbending losses. Each of the core are respectively located on the vertices of a square, the center of the square is the central axis of the multi core singlemode fiber. Each core is a single-mode optical fiber waveguides, cutoff wavelength 1.3 um.In order to reduce the bending loss and crosstalk, reinforce fiber molded capacity constraints, therefore compared with the conventional G652 optical fiber, the refractive index difference has increased. 3 core is a simple step structure, a refractive index difference 0.0062; another annular core refractive index profile, the refractive index difference 0.0l, this core is provided in order to facilitate identification of each of the cores.

The main advantage of multi-core Single Mode Fiber Cable

1. Attenuation coefficient

By the testing and research of nearly 200km long fiber , the attenuation coefficient of the multi core singlemode optical fiber reached levels close to the corresponding single core fiber.

2. Bending and micro-bending loss characteristics

Bending and microbending loss characteristics of the multi-core single-mode fiber optic is good, negligible additional loss introduced. This is due to the higher refractive index and limit the ability of a strong mold. Multi core single mode fiber optic in the l310nm and 1550nm wavelength mode field diameter was 8.4 ± 0.21un and 9.75 ± 0.25um, slightly smaller than the ordinary single mode optical fiber.

3. Crosstalk characteristics

To 30 g of tension around 15 cm in diameter optical fiber on ferrule l0 km optical fiber with characteristic measurement, crosstalk between each core at l 310 nm wavelength, less than-70dB; at 1 550 nm wavelength, less than a 50 dB, are excellent -35 dB in the required index. Even slim to the 30 km, between 0-30g tension variations, changes, crosstalk is also only a few dB.

4. Mechanical strength

Wth 10m length test, the average intensity of 70N. The conventional 125um fiber diameter of 60 N, it is because a large cross-sectional area of multi-core single-mode fiber. Fracture stress 4.6 GPa, 94% for the conventional 125 um diameter fiber.

# CWDM DWDM Networking Solutions

Wavelength division multiplexing is a cost effective and efficient way for expanding the fiber optic transmission capacity, because it allows using current electronics and current fibers and simply shares fibers by transmitting different channels at different color (wavelength) of light.

Wavelength Division Multiplexing, WDM is a technique that multiplexing several signals over a single fiber optic cables by optical carriers of different wavelength, using light from a laser or a LED. According to the number of wavelengths it supports, there are Coarse Wavelength Division Multiplexing (CWDM) and Dense Wavelength Division Multiplexing (DWDM).

CWDM was introduced as a low-cost approach to increasing bandwidth utilization of the fiber infrastructure. By using several wavelengths/colors of the light, 18 channels are viable and defined in the ITU-T standard G.694.2. CWDM systems typically provide 8 wavelengths, separated by 20nm, from 1470nm to 1610nm.

Benefits of CWDM
Passive equipment that uses no electrical power
Extended Temperature Range (0-70C)
Much lower cost per channel than DWDM
Scalability to grow fiber capacity with little or no increased cost
Protocol Transparent
Simple to install and use

Drawbacks of CWDM
16 channels may not be enough
Passive equipment offers no management capacities

DWDM packing WDM channels denser than in CWDM systems, 100 GHz spacing (approx. 0.8nm), more channels and higher capacity can be achieved using DWDM. IUT-T recommendation G.694.1 defines the DWDM channels spectrum. DWDM comes in two different versions: an active solution and a passive solution. An active solution is going to require wavelength management and it a good fit for applications involving more than 32 lines over the same fiber. In most cases, passive DWDM is looked at as a more realistic alternative to active DWDM.

Benefits of DWDM
Up to 32 channels can be done passively
Up to 160 channels with an active solution
Active solutions typically involve optical amplifiers to achieve longer distances

Drawbacks of DWDM
DWDM is very expensive
Active solutions require a lot of set-up and maintenance expense
“Passive” DWDM solution still requires power

By optical add/drop multiplexing techniques, wavelength channels may be added and dropped at intermediate nodes using passive optical components only. Optical Add/Drop Multiplexers are used in WDM Systems for multiplexing and routing fiber optic signals. They can multiplex several low-bandwidth streams of data into a single light beam, and simultaneously, it can drop or remove other low-bandwidth signals from the stream of data and direct them to other network routers. There are CWDM OADM and DWDM OADM.

FiberStore offer a wide range of WDM optical networking products that allow transport of any mix of service from 2Mbps up to 200Gbps. Our highly reliable WDM/CWDM/DWDM products include CWDM multiplexers and demultiplexer, DWDM Multiplexers and demultiplexers, CWDM & DWDM Optical Add-drop Multiplexer, Filter WDM modules, CATV amplifier, OEO converters as well as many other most demanding CWDM DWDM networking infrastructure equipment.

# Why Choose the Shielded Cabling System

Shielded VS. Unshielded Cabling

In copper structured cabling system at all levels, there are two main technical types: Shielded and Unshielded cabling systems. Both types have been in existence since the earliest cabling standards were defined. While shielded cabling became popular from the outset in countries like Germany, Austria,Switzerland and France, U/UTP was quickly adopted in the rest of the world. Although both systems work fine at 1 Gigabit Ethernet data rates, shielded systems can demonstrate superior performanceat higher data rates such as 10G due to their ability to reliably support higher frequency transmission.

What Is the Function of Shielded?

F/UTP

F/UTP cable shielding structure is four pairs of wires in the data cable outside the contractor a layer of aluminum foil shielded, this layer of shielding can be reduced to a great extent the total package:

This is the root of the signal transmission cable radiated interference signals on the impact of adjacent data cable (for example: the same bundle of cables in the adjacent data cable).Interference from other data cable or other interference source signal for this cable.For a high quality data transmission system, which is significant in two kinds of effects. If the external interference signal is strong enough it will happen with the normal transmission signal stack a plus, resulting in reduced transmission performance even the entire system can not work properly.

S/FTP

S/FTP structure in addition to the total package of braided foil shield, twisted pair cable are respectively in each pair with a layer of aluminum foil shield to protect the transmission signal does not interfere with each other, so near-end crosstalk attenuation (NEXT)performance dramatically. NEXT better performance means higher SNR and better transmission quality and faster system output. S/FTP shielded cables NEXT excellent structural performance of other cables (such as non-shielded U/UTP) can not be compared, therefore, ISO11801 on the Cat 7 (600MHz) and Cat 7a  (1000MHz) only provides the S/FTP cable structure, U/UTP cannot meet.

10GBase-T Makes Data Cable Face New Problem: Alien Crosstalk

2006 Copper Gigabit Ethernet applications published the proposed new standard transport protocols 10GBASE-T. Compared to 1000Base-T, its transmission rate increased 10 times. 1000BASE-T copper cabling required parameters (Attenuation, NEXT, Return Loss, etc.) the bandwidth required to reach 1-100MHz, with UTP Cat 5e (Class D) cabling system to meet requirements. 10GBASE-T cabling channel requirements of all component parameters have to be up to 500MHz bandwidth, which requires copper to reach at least Cat.6A (Class Ea) or higher level.

Along with the development of 10GBASE-T, external noise problems become more evident, resulting in a specification for external noise to be used to assess in the same bundle of cables, the interaction between different cables. This is what we call Alien Crosstalk. Alien Crosstalk will increase with the increase of frequency. Worse, 10GBASE-T confronted with external noise, will not be able to “adaptive” to lower the rate at which the network may be subsequently face paralysis. Therefore, to support 10GBASE-T cabling system application, the ability to resist alien crosstalk is vital.

Since 10GBASE-T high transmission frequencies and complex coding method is very sensitive to the external noise. Shielding system excellent coupling atttenuation performance makes it naturally have to resist alien crosstalk.The unshielded system against alien crosstalk is usually only on the performance of 0dB.Shielding system in the design is completely satisfy the application of 10G.

The Installation of 10GBase-T: U/UTP VS. FTP 80a

Unshielded System

As far as possible away from power cable during installationDifferent applications (1Gb/s and 10Gb/s) in the same pipeline transmission will cause the external crosstalk.

Shielding System

With the power cable can be reduced separation distanceAllow different applications (1 Gb / s and 10 Gb / s) in the same pipeline transmissionDoes not need additional external crosstalk test field

The Separation Distance Between the Data Cable and Power Cable

In EN50174 standard defines the content of different coupling attenuation value level of data cable, respectively, from A (low coupling attenuation, worse) to D (high coupling attenuation, good) four levels.

Classification of information technology cables

 Screened Unscreened Coaxial/twinaxial Segregation classification Coupling attenuation at 30 Mhz to 100 Mhz TCL at 30 MHz to 100 MHz Screening attenuation at 30 MHz to 100 MHz >= 80a dB >= 70 -10xlg(f) dB >= 85d dB d >= 55b dB >= 60 -10xlg(f) dB >= 55 dB c >= 40 dB >= 50 -10xlg(f)c dB >= 40 dB b < 40 dB <50 -10xlg(f) dB < 40 dB a

Installers need to know which cable separated levels to determine the choice of the data requirements of the standard cable with power cable between the minimum separation distance. Data cable coupling attenuation higher the value and power cables minimum separation distance between the smaller. Please refer to the following three examples, screenshots from Nexans Toolkit.

Example 1: U/UTP (Class B – Coupling Attenuation >/= 40dB) -> 225mm

Example 2: F/UTP (Class C – Coupling Attenuation >/= 55dB)-> 114mm

Example 3: S/FTP (Class D – Coupling Attenuation >/= 80dB)-> 24mm

Relative to the shielded cable, the unshielded (U/UTP) separation distance between cable and power cable to further. In the implementation of the project, if need the data cable and power cable isolation far distance, we need a bigger size pipe/bridge, or even additional bridge, doing this will no doubt have higher cost, sometimes limited to the bridge installation space. To make matters worse, these additional requirements often neglected or ignored, resulting in network system is the key point of interference.

Grounding

For shielded, unshielded systems and fiber optic cable, all need to implement protective grounding. Because of the need to consider personal and equipment safety, therefore no matter adopt what kind of cabling system, the metal part of the system must be grounded. For the shielding system, also need to implement the functional ground. Grounded shielding system functions with respect to the implementation of non-shielded systems only difference is that when you install the module connector and the cable shielding mask area area connected.

Conclusion

Shielding system relative to the unshielded system has been greatly improved EMC performance. For Gigabit Ethernet applications, shielding against external interference effects is essential, and shielded cabling system had to meet the standards in the design of anti-alien crosstalk (A-XT) requirements, can effectively prevent the cable from the adjacent between the external crosstalk. Shielded cabling system, properly grounded at both ends of the case, to resist external interference characteristics superior to unshielded system 40dB.

# Cabling Design and Thinking

Introduction

As all we known: cabling of building local area network (LAN) at the end of the 100m cabling, community area last 2km integrated network cabling computer data center room, such as several internal cabling. Cabling in different locations, in accordance with their purpose and corresponding transmission index calculating the length of the cabling to allow laying. No matter what position cabling used, all belong to the city telecommunications network extension and an important part. Only in depth understanding of urban development trends of telecommunication networks, in order to accurately grasp how to design integrated cabling; also only be taken with the city development strategy telecommunication network synchronization and with suitable, cabling can really play the overall effectiveness of the network and obtain win-win enconomic effects. Here only to the development of telecommunication networks, cabling should be synchronized with the development, as well as the latest developments in cabling issues such as study and discussion.

The development trend of telecommunication network

In traditional telecommunications networks based voice communication, a small amount of digital data network (DDN), Frame Relay (FR) point to point, such as low rate of data communication, a voice path begins only within the bandwidth of 64kbps. In the early 1990s, China’s foreign experience with the introduction of Ethernet Cable Wiring and network communication technology, and accordingly developed our standards, and actively promote the application of the telecommunications network to get great propress. In just 10 years time, network communication technology from 10 megabytes, 100 megabytes, Gigabit to 10 Gigabit-class development, or even 10 Gigabit-class network will soon put into large-scale application.

The development of the telecommunication network is omni-directional, methods of communication include: wired, wireless, satellite, etc.; Communication contents include: telephone, television, data, etc..

a. The rapid development of the passive optical network (PON)

Currently, the passive optical network (PON) is rapidly developing country, for example: EPON (Ethernet Passive Optical Network), GPON (Gigabit Passive Optical Network), GEPON (Gigabit Ethernet Passive Optical Network), APON (ATM Passive Optical Network), BPON (Broadband Passive Optical Network) and other network applications, structured cabling will have a direct impact. Now illustrate EPON/GPON networking mode:

EPON/GPON is mainly composed of OLT (Optical Line Terminal), ODN (Optical Distribution Network) and ONU (Optical Network Unit) and other components. EPON / GPON networking shown in Figure 1:

The network characteristics of EPON/GPON:

* On the OLT and ONU in addition to optical interface, combined with GE (Gigabit Ethernet), FE (Fiber optic Ethernet), RF (Radio Frequency), E1 (2.048Mbps) interfaces, can be applied to various network applications.

* GPON can provides uplink 155Mbps, 622Mbps, 1.24Gbps or 2.48Gbps; Downlink 1.24Gbps or 2.48Gbps.

* Public IP network signal WDM CWDM DWDM, the uplink of 1490nm and downlink of 1310nm signal through the central office OLT integrated transceivers were injected into the same optical fiber, through the optical distribution network ODN spending 32.64 points or 128 optical link to the corresponding ONU. If necessary, can also be injected CATV signals using the third wavelength of 1550nm central office OLT transceiver integrated in the corresponding ONU than the client integrated transceivers separated by the RF interface of the user received a cable distribution network.

* EPON/GPON network support tree, star, bus, hybird and redundant topology etc..

* EPON is based on the standard Ethernet technology and IEEEP802.3ah, in the case of transport 1.25Gbps data stream, the optical line terminal (OLT) and the optical network terminal (ONU) between a transmission distance up to about 20km.

* GPON is based on the ITU-T standard G984.1-G984.5 version, is preferred in Europe and North America, FTTH technology, is being used worldwide. GPON generic framing protocol that provides a multi-protocol transmission efficiency can provide an open interface, with 2.48Gbps rate symmetric and asymmetric transmission capacity, OLT/ONU transmission distance up between 37km.

b. FTTH or FTTB/N

As EPON/GPON technology matures, the price of Optical Fiber Cable are more and more cheap. Fiber optic cable extends to the floor, community nodes, and even to the family increasingly likely. As telecom companies certainly want to consider the relationship between input and output in the short term cost recovery and profit is the ultimate goal.

1. Provide greater bandwidth capacity, suitable for high speed network applications.

2. Is not affected by the outside electromagnetic interference, anti-interference performance is good, high quality communications.

3. Silica fiber material production inexhaustible.

4. The price of fiber optic cable has lower than copper (but photoelectric conversion equipment price is still relatively high, therefore, the overall cost is higher).

1. Same scale projects, the initial investment is higher.

2. New fiber optic cable and more, longer construction period (relative to the FTTB/N solution).

3. Slow return on investment.

The rapid development of the Internet age, fiber optic modem is good for you, especially when you’re dealing with large amounts of data.Fiber optic modems,someone also called fibre optic modems.This type of modem, you can quickly and efficiently transfer data.Under normal circumstances, the fiber optics modem provides two modes of multi-mode and single-mode.

Fiber optics modem receives the incoming optical signal by optical fiber cable, and translate them back to the electronic form of full-duplex transmission. They are available in single channel and multi-channel configuration.FiberStore fiber optic modems are available in various form factors depending upon the protocol selected, such as RS-232/RS-485/RS-422 Fiber Optic Modem. Our FOM has a higher bandwidth and greater electromagnetic immunity than wire-based modems. Together with multimode or single-mode fiber, the fiber optic modem allows data to be transmitted and convert electrical signals to light. It provides transmission distance up to 2km (multimode) or up to 20km/40km/60km (single-mode).

The FOM allows users to replace existing coaxial cable communication links with lightweight fiber optic cable. The advantages of using fiber optic cables are as follow:

1) Lighter weight and smaller size for much quicker deployment
2) Higher bandwidth for increased throughput
3) Lower loss for long distance repeater less communication up to 16 kilometers
4) Better quality-safe from electromagnetic interference from any source
5) More secure – no electromagnetic signature
6) Less expensive

Note:Fiber optic modem is the new kid on the block as it joins cable, DSL, satellite and dialup in the battle for Internet access superiority. Although it’s not available in all areas, its higher speeds and reliability make it a major contender. Internet or network connections that require a fiber optic modem are more commonly used commercially rather than residentially. Not all Internet service providers offer a fiber optic option, so the first step to choosing a fiber optic modem is to make sure you actually need one. Most home Internet connections use copper wires and coaxial cables, though these may connect to fiber optic wiring at the curb. Check with your Internet provider to see what types of modems can work with your particular service.