Which Fiber Optic Connector should you use?

The network cabling industry’s fiber optic manufacturers over the last few decades have been on a constant mission to develop the better fiber connector. This means lower cost, lower dB losses, easier to terminate out in the field. There have been over 100 connectors developed over the years but a select few have stood the test of time and beat out their competition. Below we will talk about the most common.

 

A fiber optic connector terminates at the end of a fiber optic cable and is used when you need a means to connect and disconnect the fiber cable quickly. A fiber splice would be used in a more permanent application. The connectors provide a mechanical connection for the two fiber cables and align both cores precisely so the light can pass through with little loss. There are many different types of connectors but many share similar characteristics. Many connectors are spring loaded. This will push the fiber ends very close to each other so as to eliminate airspace between them, which would result in higher dB losses.

 

There are generally five main components to a fiber connector: the ferrule, the body, the coupling structure, the boot and the dust cap.

 

Ferrule-the ferrule is the small round cylinder that actually makes contact with the glass and holds it in place. These are commonly made of ceramic today but also are made of metal and plastic.

 

Body-This sub assembly holds the ferrule in place. It then fits into the connector housing.

 

Connector Housing-This holds all sub assembly parts in place and has the coupling that will connect to the customer’s equipment. The securing mechanism is usually bayonet, snap-in or a screw on type.

 

Boot-This will cover the transition from the connector to the fiber optic cable. Provides stress relief.

 

Dust Cap-Just as it implies will protect the connector from accumulating dust.

 

There are many types of connectors on the market. The major differences are the dimensions and the method of connection to equipment. Most companies will settle on one type of connector and keep that as a standard across the board. It makes sense because all equipment has to be ordered with that specific connector type and to have 2 or 3 different connector types can get messy. For typical network cabling projects today LC is fast becoming the shining star of fiber connectors. LC is a small form factor connector which means it requires a much smaller footprint in your IT closet. Thus you can fit many more LC connectors into you fiber panels then say ST or SC connectors.

 

ST Connector

 

 

The ST connector (or Straight Tip) was the first popular connector type to be used as a standard for many organizations in their fiber network applications. It was first developed by AT&T. Often called the “round connector” it has a spring loaded twist bayonet mount with a 2.5mm round ferrule and a round body. The ST connector is fast being replaced with the smaller, denser SFF connectors.

 

SC Connector

 

The SC connector is a push-in/pull-out type connector that also has a 2.5 mm ferrule. It is very popular for its excellent performance record. The SC connector was standardized in TIA-568-A, and has been very popular for the last 15 years or so. It took a while to surpass the ST because of price and the fact that users were comfortable with the ST. Now it’s much more competitive with pricing and it is a very easy install, only requiring a push in and pull out connection. This is very helpful in tight spaces. Simplex and duplex SC connectors are available. The SC was developed by the Japanese and some say stands for Standard Connector.

 

FDDI/ ESCON Connectors

 

You may see FDDI and ESCON(IBM) duplex fiber connectors in older installations. These connectors will mate to their own networks and usually will be seen at the wall outlet locations. These connectors use a squeeze tab coupling mechanism. The closet side of the fiber will usually have a standard ST or SC connector. The FDDI/ESCON connectors can be mated to SC or ST connectors since they both have a 2.5mm ferrule. An adaptor would be required in this case. The FDDI stands for Fiber Distributed Data Interface.

 

LC Connector

 

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The LC connector was developed by Lucent Technologies, hence the LC. It is a Single Form Factor Connector that has a 1.25mm ferrule. The attaching mechanism is similar to an RJ-45 connector with the retaining clip. It is a smaller square connector, similar to the SC. LC connectors are often held together with a duplex plastic retainer. They are also very common in single mode fiber applications.

 

MT-RJ Connector

 

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MTRJ stands for Mechanical-Transfer Registered Jack and was developed by Amp/Tyco and Corning. MTRJ is very similar to an RJ type modular plug. The connector is always found in duplex form. The body assembly of the connector is usually made from plastic and clips and locks  into place. There are small pins present that guide the fiber for correct alignment. MTRJ’s  also are available in male or female orientation. They are only used for multi-mode applications. They can also be difficult to test because many testers on the market do not accept a direct connection. You usually need to rig up a patch cord adapter kit to make testing possible.

 

FC Connector

 

The FC connector you may find in older single mode installations. It was a popular choice that has been replaced by mostly ST or SC type connectors. It also has a 2.5mm ferrule. They have a screw on retaining mechanism but you need to be sure the key and slot on the connector are aligned correctly. FC connectors can also be mated to ST & SC’s through the use of an adaptor.

 

Opti-Jack Connector

 

The Opti-Jack is a clean, tough duplex connector cleverly designed around two ST-type ferrules in a package the size of a RJ-45. It has male and female (plug and jack) versions.

 

 

LX-5 is like a LC but with a shutter over the end of the fiber.

 

MU Connector

 

MU looks a miniature SC with a 1.25 mm ferrule. It’s more popular in Japan.

 

MT Connector

 

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MT is a 12 fiber connector for ribbon cable. It’s main use is for preterminated cable assemblies and cabling systems. Here is a 12 fiber MT broken out into 12 STs.

This connector is sometimes called a MTP or MPO which are commercial names.

 

Hopefully this guide may help you get an idea of what options are out there for your fiber optic connector needs.

 

As always, for all your fiber optic needs go to http://www.fiber-mart.com

How to Troubleshoot a Faulty PON With an OTDR

It is easy to trouble shoot the failure which occurs on a point-to-point FTTx network by using an optical time domain reflectometer (OTDR) test. However, troubleshooting a faulty point-to-multipoint network (i.e. PON network) differs significantly and are more complex than a point to point network. This post will introduce the potential faults which may occur in a PON, and explain how to troubleshoot them with an OTDR.

 

Brief Introduction of PON

A PON (passive optical network) is a telecommunications network that uses point-to-multipoint fiber to the premises in which unpowered optical splitters are used to enable a single optical fiber to serve multiple premises. A basic PON (see Figure 1) consists of an optical line terminal (OLT) at the service provider’s central office and a number of optical network termination (ONT) or optical network units (ONUs) near end users. Sometimes, a second splitter can be connected in cascade to the first splitter to dispatch services to buildings or residential areas (see Figure 2). The International Telecommunications Union (ITU-T) and Institute of Electrical and Electronic Engineers (IEEE) have created several standards for optical access systems based on PON architecture (G.982, G.983 or G.984 for ITU and 802.3ah or 802.3av for IEEE).

 

Figure 1. Simple PON Topology

 

Figure 2. Cascaded PON Topology

Due to its architecture, operators can easily determine which subscribers are affected, and can also identify possible fault elements such as how many customers are affected and whether the PON is cascaded by using the network monitoring system at the Network Operation Center (NOC).

Possible Scenarios & Potential Faults of a PON

 

In general, we divide the faulty case of a PON as three scenarios. One case is that only one customer is affected. And the other case is occured in the cascaded PON and all affected customers are connected to the same splitter. The last case is all customers dependant on the same OLT are affected whether the PON is cascaded or not. In the first case, there are three probable potential faults. Fault may appear in the distribution fiber between the cutsomer and the closest splitter, or in the ONT equipment, or even appear in the customer’s home wiring. See Figure 3 (a) & (b).

 

Figure 3 (a). PON Case 1—Possible Faults When Only One Subscriber is Affected

 

Figure 3 (b). PON Case 1—Possible Faults When Only One Subscriber is Affected

When all customers connected to the same splitter cannot receive service, but others connected to the same OLT can, namely the second case, the cause may be that there is a fault at the last splitter or in the fiber link between the cascaded splitters. See Figure 4.

 

Figure 4. PON Case 2—Cascaded PON with Affected Subscribers Connected to Last Splitter

To the thrid case described above, if all customers are affected, the fault may occur in the splitter closest to the OLT, or in the feeder fiber/cable of the network, or directly in the OLT equipment, as the Figure 5 shown.

 

Figure 5. PON Case 3—All Subscribers are Affected (All Connected to the First Splitter)

In addition, we should know that if connectors are available at the splitters, terminals, or drops, isolating part of the faulty network will become easier. Inspecting connectors and taking OTDR measurements using 1310/1550 nm wavelengths are often performed on network sections that are out of service.

 

Why Use The Specific In-service Portable OTDR Device?

In order to troubleshoot PON networks in service, two dedicated tools are available — PON power meter and In-service 1625 or 1650 nm OTDR. As we know, a PON power meter is normally employed to verify that the signal is transmitted correctly to and from the ONT. A PON meter measures the power levels of all the signals and can then discriminate whether the issue comes from the customer’s ONT or from the network. However, you might be very confused with that why use In-service OTDR. The use of a classical OTDR with 1310 or 1550 nm test wavelengths would interfere with the traffic signals and disturb the traffic. At the same time, the traffic signals could also disturb the receiver of the OTDR, making it difficult to interpret OTDR traces. Due to mutual disturbances, classical OTDRs cannot be used, and specific in-service OTDRs are required.

The in-service OTDR was designed specifically for testing live fiber networks. This dedicated device uses an out-of band wavelength (test wavelength far away from traffic wavelength) to enable OTDR testing without disturbing either the network transmitters or the receivers. In the case of a PON network, WDM is no longer needed, except for monitoring purposes (using a remote fiber test system). The PON network is a point-to-multipoint configuration and the troubleshooting test is performed directly from an accessible element (ONT or splitter). The operator can disconnect the element because service is already off downstream toward the customer. First, the in-service OTDR must not disturb the other customers while shooting the OTDR test wavelength upstream toward the OLT, which is most likely the case, as OLTs reject signals above 1625 nm, based on ITU-T recommendations. Second, the traffic signals that the OTDR receives will be rejected to obtain accurate OTDR traces. The specific long-pass filter used to protect the OTDR diode can be added either via a jumper between the OTDR and the network or built into the OTDR.

 

Most equipment providers enable the use of the 1625 nm wavelength for safe testing. Some countries, such as Japan, are nevertheless pushing the 1650 nm wavelength as reflected in the ITU-T L.41 recommendation, which provides maintenance wavelengths on fiber-carrying signals. The 1650 nm wavelength is preferred based on the design of the filters and also because it is further away from the traffic signals (current and future PON technologies).

Case of PON Troubleshooting with OTDR

 

In order to make the whole troubleshooting or testing work smothly, it is essential to select the right OTDR tool, the correct pulse width, and the best location to start troubleshooting. OTDR configuration should be set according to the equipment being qualified and the distance to cover.

 

In response to the possible scenarios and potential faults of a PON described above, here are some solutions with OTDR to be introduced in the following. To avoid complexity, this document only analyzes the cases where connectors are only available at the ONT/OLTs.

 

Solution 1: Troubleshooting of the Distribution Fiber

Simple PON—Only one subscriber affected. Consider that no connectors are available at the splitter.(see Figure 6)

Case Test Location OTDR Direction What must be Seen Comment Pulse Width to be use Specific OTDR

Case 1 one customer down Customer’s home Disconnect the ONT Upstream Distribution fiber up to the closest splitter Testing through the splitter is not required, as the issue is only on the disrtibution fiber side. Short pluse 3 to 30 ns In-service OTDR

 

Figure 6. OTDR is Shot Upstream and Trace only Matters up to the Splitter

Solution 2: Troubleshooting of the Distribution Fiber and the Fiber between the Two Splitters in case of a Cascaded Network

All customers linked to the second splitter are down. Let’s consider the case where no connectors are available at the splitter.(See Figure 7.)

Case Test Location OTDR Direction What must be Seen Comment Pulse Width to be use Specific OTDR

Case 2 all the customers are down after the second splitter Customer’s home Disconnect the ONT Upstream Distribution fiber up to the two splitters Testing through the closest splitter is required. Medium pluse 100 to 300 ns In-service OTDR – short dead zone

This case requires viewing the signal after the splitter. The OTDR used must be optimized for this application and have the shortest possible dead zone as the splitter typically provides 7 to 10 dB loss.

 

Figure 7. OTDR is Shot Upstream and Trace should Display the Traffic through the Last Splitter up to the First One

Solution 3: Troubleshooting of the Feeder

Information received at the NOC shows that all customers are down. As the problem likely comes from the feeder side, the most common way to test the faulty network is to shoot an OTDR downstream from the OLT.(See Figure 8.)

Case Test Location OTDR Direction What must be Seen Comment Pulse Width to be use Specific OTDR

Case 3 all customers are down OLT Downstream Feeder Testing through the splitter is unnecessary. Short pluse 3 to 30 ns Unnecessary

 

Figure 8. OTDR is Shot Downstream and Trace should Display the Traffic Down to the First Splitter

Note: OTDR testing directly from the OLT is certainly the preferred choice when a faulty feeder is suspected (Solution 3), but this method is not recommended in the other cases.

SFP to 16x10/100Base-T RJ-45 Industrial Managed Media Converter

4x10/100/1000Base-X SFP to 16x10/100Base-T RJ-45 Industrial Managed Media Converter

Media converters can be used anywhere in the network to integrate newer technology with existing equipment to support new applications, technologies and future growth. Instead of costly, across-the-board upgrades, media converters can extend the productive life of the existing cabling as well as the active equipment.

Fiber-Mart supply 10/100Base Ethernet Fiber Media Converters, 1000Base Gigabit Fiber Media Converter, SFP Fiber Media Converter, Industrial managed Media Converter, Managed Media Converter, POE media Converter, options in singlemode dual fiber, multimode dual fiber and singlemode single fiber. We also supply Media Converters Chassis, like 14 slot media converter chassis and 16 slot media converter chassis, used to manage the various media converters.
 

Key Features

• 4 SFP 10/100/1000 Ports, 10/100Mbps auto-negotiation UTP Ports
• Supports Full/Half Duplex, auto-negotiation, MDI/MDI-X on TX ports
• Support Web Management
• Support Vlan and QoS
• Support OP Ring Protection (OPRP) and recovery within 30ms
• Relay alarm for port breakdown
• Reliable and stable performance
• Free fall, Shock and Vibration Stability
• Standard: IEEE802.3, IEEE802.3u, IEEE802.3x, IEEE802.3z, 10/100Base-TX, 100Base-FX, 10/100/1000Base-TX, 1000Base-FX/LX

Specifications

The Industrial web managed media converter enables network administrators to easily monitor and setup the converter, the transmission speed and duplex through web browsers. Build an ISP network solution of FTTH (Fiber to the Home), FTTC (Fiber to the Curb) for ISPs, or FTTB (Fiber to the Building) for small office network environment in the enterprises.

Note: Port Base VLAN is optional, please contact sales@fiber-mart.com for more details.

• MAC address: 8K
• UTP port: 16-ports RJ45
• UTP Rate: 10/100Mbps
• UTP cable: Cat. 5 (the max distance up to 100m)
• Multimode Fiber: 50/125, 62.5/125μm(the max distance up to 224/550m)
• Single-mode Fiber:9/125μm single-mode cable, provides long distance for 10/15/20/30/40/50/60/70/120km (very on fiber transceiver or SFP module)
• Input Voltage: 18- 36V DC, Redundant dual power input
• Operation Temperature: -10 ℃~60 ℃(Humidity: 5~90% non-condensing)
• Storage Environment: -20℃~+85℃ (Humidity: 5~90% non-condensing)