Category: Fiber Transceivers

The requirements for testing fiber optic networks will vary depending on the specific type of network as well as the network designer’s overall test requirements. Regardless of type, there are two basic or generic pieces of Optical Test Equipment that will be used; an Optical Time Domain Reflectomer or OTDR, and a pair of optical test equipment pieces that are referred to as a Power Meter & Light Source. These tests are typically measured in “dB”. The term dB is the expression of attenuation or power loss over an optical fiber as it travels from a termination end to a point along the fiber’s path. Once an optical fiber is connected to a piece of active equipment then all tests are in dBm. The active equipment will be transmitting an actual or real optical power at a specific wavelength and referenced at 1mW.

A PON power meter is essential for field technicians installing or maintaining any type of PON network. PON Power Meters are able to simultaneously test upstream and downstream through optical fibers, at 1490nm, 1550nm, and 1310nm wavelengths, as well as estimate signals of the voice, data, and video streams.

The term PON stands for “passive optical network”. A PON is a fiber optic telecommunications network that delivers broadband to transmit data over fiber optic cables to the customer premises. Its architecture implements a point-to-point or a point-to-multipoint arrangement of nodes in a communications network. A Point-to-Multipoint network uses a single fiber to serve multiple endpoints by using unpowered or passive fiber optic splitters. A splitter is used to divide the fiber bandwidth among multiple access points. Passive optical networks are often referred to as the “last mile” between an internet service provider (ISP) and its customers.

Point-To-Point or P-T-P type optical network

A P-T-P network is a network that has two termination points and nothing in-between. As with all fiber optic networks, when it is being constructed the fibers must be terminated to allow for any tests to be performed. So one end of the network is terminated and an OTDR test is performed on each fiber to ensure that the termination and length of fiber beyond does not have any issues. That test result will be stored for future needs and noted in “dB”. If the network requires splicing then after the fibers are spliced, the OTDR again is used to ensure that the splice and added fiber length again meets requirements. The testing with the OTDR continues and is completed after the end of each fiber is terminated. At this point, another set of tests is required which is commonly referred to as an End-To-End test. This test requires the use of a light source and a power meter and again all test results are stored. The optical power meter will be set to “dB” and referenced to a light source which is typically called “Zeroing”. The units are then moved to opposing ends and the field technicians will send and receive wavelengths specified by the designer. Again this is a measurement that will be used against the designer’s overall Link Loss Budget. The P-T-P network will have its termination ends referred to as “A” and “B” and at least two unique wavelengths will be sent and received over each fiber. This is typically required to ensure that any wavelength used by a transmitter can be used between the two that are specified. The network designer will define these wavelengths as well as provide a label for these ends. The technician that is performing the tests will reference these labels in any reporting back to the designer.

Point-To-Multipoint PON type network

Now when a Point-To-Multipoint network is constructed such as a Passive Optical Network or PON many of the tests and test equipment remain the same but will require a few special features. The OTDR testing during construction remains the same, with tests performed each time a fiber is terminated or spliced. Again, this continues to the far ends of the fibers after they are terminated. Once all fibers are terminated, again they will be tested using a power meter and light source. The need for special equipment is required for the activation phase of a PON network and that’s where the similarity between a P-T-P and a P-T-Multipoint ends.

The PON network activation phase begins by connecting a power meter up to an active piece of equipment called an Optical Line Terminal or OLT and set to the appropriate wavelength and the unit is set to “dBm” and this becomes the referenced power.

NOTE: There are several generations of PON network OLTs which use different wavelengths so the optical power meter must have the capability to be set to those wavelengths. GPON is 1490nm, XGPON is 1577nm and NGPON has multiple wavelengths ranging from 1596nm to 1602nm.

As the links are connected out to the far end, the technician repeats the test and ensures that there are no issues. This testing continues out to the far end, which in a PON network there is a piece of active equipment called an Optical Network Terminal or ONT or at times called an Optical Network Unit or ONU. Regardless, that piece of equipment receives light from the OLT transmitter and communicates back to the OLT with its own transmitter. The ONT cannot communicate back to an OLT without first receiving the OLT’s transmitter’s wavelength. At this time, there is an absolute need to use a specialized optical power meter which can measure the OLT’s power and allow that power to pass through and provide the signal to the ONT/ONU so it can send back a signal.

The PON meter has two test ports; one is named DROP and the other ONT or ONU. The technician connects the drop, which is connected via a fiber all the way back to the OLT into the port named DROP and then connects the ONT/ONU connectorized fiber pigtail into the ONT/ONU port. Now the PON meter is in-line between the OLT and ONT/ONU and allows for the OLT to communicate with the ONT/ONU. The technician again will be observing the incoming OLT power level, as well as the outgoing ONT/ONU power level. If all is well, the drop is connected to the ONT/ONU and service activation tasks can continue.

I hope you have found this article informative and that you learned a bit about FTTx networks.

This special fiber patch cord is a duplex multimode patch cable that has a small length of single mode fiber at the start of the transmission length. It is designed to solve the technical issue involved in using single mode equipment on the existing multimode cable plant. Mode conditioning fiber patch cord aims to drive the distance of installed fiber plant beyond its original intended applications, as well as to improve data signal quality.

Optical Mode Conditioners provide a convenient and reliable method of connecting multimode fiber plants with 1000Base- LX based transmission equipment compliant with IEEE 802.3 standards. Mode conditioners provide a method of offsetting a single-mode fiber core with a corresponding multimode fiber. This calibrated offset reduces a phenomena called differential mode dispersion, or DMD, which can cause the transmitting laser pulse to spread out and merge into neighboring pulses creating bit errors in the transmission signal.

Mode conditioners are built in the form of a simple duplex patch cable, so they can easily be installed in a system without the need for additional components or hardware. Their length can range from one meter and up to support virtually any network topography.

The need for this patch cord is due to the single-mode launch nature of the -LX (1300nm) transceiver modules used for Gigabit Ethernet. These modules have to operate for both single-mode and multimode fibers. Launching a single-mode laser into the center of a multimode fiber can cause multiple signals to be generated that confuse the receiver at the other end of the fiber. These multiple signals, caused by Differential Mode Delay (DMD) effects, severely limit the cable distance lengths for operating Gigabit Ethernet. A mode conditioning patch cord eliminates these multiple signals by allowing the single-mode launch to be offset away from the center of a multimode fiber. This offset point creates a launch that is similar to typical multimode LED launches.

Things to know when using mode conditioning cables to patch an existing multimode cable plant to your Gigabit LX equipment.

Usually used in pairs, mode conditioning cables usually require a MC cable at each end to connect the equipment to the cable plant. The only reason to order an odd number of mode conditioning cables is to have a spare on hand.

If your Gigabit LX switch is equipped with SC or LC connectors, please be sure to connect the yellow leg (single-mode) of the cable to the transmit side, and the orange leg (multimode) to the receive side of the equipment. It is imperative that this configuration be maintained on both ends. The swap of transmit and receive can only be done at the cable plant side.

In fiber optic cable installation, how cables are attached to the system is vital to the success of network. If done properly, optical signals would pass through the link with low attenuation and little return loss. Fiber optic pigtail offers an optimal way to joint optical fiber, which is used in 99% of single-mode applications. This post contains some basic knowledge of fiber optic pigtail, including pigtail connector types, fiber pigtail classifications, and fiber pigtail splicing methods.

Fiber Pigtail Specification

Fiber optic pigtail is a fiber optic cable terminated with a factory-installed connector on one end, leaving the other end terminated. Hence the connector side can be linked to equipment and the other side melted with optical fiber cables. Fiber optic pigtail are utilized to terminate fiber optic cables via fusion or mechanical splicing. High-quality pigtail cables, coupled with correct fusion splicing practices offer the best performance possible for fiber optic cable terminations. Fiber optic pigtails are usually found in fiber optic management equipment like ODF, fiber terminal box and distribution box.

Fiber Pigtail vs Fiber Patch Cord: What Is the Difference?

Fiber optic pigtail has fiber connector installed at only one end, and the other end is left empty. While both ends of a fiber patch cord are terminated with fiber optic connectors. Patch cord fibers are usually jacketed, whereas fiber pigtail cables are usually unjacketed for they are usually spliced and protected in a fiber splice tray. Moreover, patch cord fiber can be cut into two pieces to make two pigtails. Some installers prefer to do this to avoid the problem of testing a pigtail cables in the field—just test the performance of a fiber patch cord, then cutting it into halves as two fiber pigtails.

Fiber Optic Pigtail Types

Fiber optic pigtails are available in various types: Grouped by pigtail connector type, there are LC fiber optic pigtails, SC fiber pigtails and ST fiber pigtails, etc. By fiber type, there are single-mode fiber optic pigtail and multimode fiber optic pigtail. And by fiber count, 6 fibers, 12 fibers optic pigtails can be found in the market.

By Fiber Type

Fiber optic pigtails can be divided into single-mode (colored yellow) and multimode (colored orange) fiber. Multimode fiber optic pigtails use 62.5/125 micron or 50/125 micron bulk multimode fiber cables and terminated them with multimode fiber optic connectors at one end. 10G multimode fiber cables (OM3 or OM4) are also available in fiber optic pigtails. The jacket color of 10G OM3 and OM4 fiber optic pigtail is usually aqua. Single-mode fiber pigtail cables use 9/125 micron single-mode fiber cable and terminated with single-mode fiber connectors at one end.

By Connector Type

According to different types of pigtail cable connector terminated at the end, there are LC fiber pigtail, SC fiber pigtail, ST fiber pigtail, FC fiber pigtail, MT-RJ fiber pigtail, E2000 fiber pigtail and so on. With different structures and appearance, each of them has their own advantages in different applications and systems. Let’s go through some widely used ones.

SC Fiber Optic Pigtail: SC pigtail cable connector is a non-optical disconnect connector with a 2.5mm pre-radiused zirconia or stainless alloy ferrule. SC fiber pigtail is economical for use in applications such as CATV, LAN, WAN, test and measurement.

FC Fiber Optic Pigtail: FC fiber pigtail takes the advantage of the metallic body of FC optical connectors, featuring the screw type structure and high precision ceramic ferrules. FC fiber optic pigtails and its related products are widely applied for the general applications.

ST Fiber Optic Pigtail: ST pigtail connector is the most popular connector for multimode fiber optic LAN applications. It has a long 2.5mm diameter ferrule made of ceramic (zirconia), stainless alloy or plastic. Hence SC fiber pigtails are commonly seen in telecommunications, industry, medical and sensor fields.

Like fiber optic patch cords, fiber optic pigtails can be divided into UPC and APC versions. Most commonly used types are SC/APC pigtail, FC/APC pigtail and MU/UPC pigtail.

By Application Environment

Some pigtail cables are specially installed to withstand the harsh or extreme environments, so here comes armored fiber pigtail and waterproof fiber pigtail.

Armored Pigtail: enclosed with stainless steel tube or other strong steel inside the outer jacket, armored fiber optic pigtails provide extra protection for the fiber inside and added reliability for the network, while reduce the unnecessary damage caused by rodents, construction work, weight of other cables.

Waterproof Pigtail: designed with a stainless steel strengthened waterproof unit and armored outdoor PE (Poly Ethylene) jacket, waterproof fiber pigtail is a great fit in harsh environments, like communication towers, CATV and military. Waterproof pigtail cable boosts good toughness, tensile and reliable performance, facilitating the use in outdoor connections.

The biggest problems that arise from optical fiber networks are the troubles with connecting them. This is why we look for efficient methods which will help us better troubleshoot problem areas in the cables. One such product is a Visual Fault Locator.

A Visual Fault Locator is a very important part of the installation and maintenance kit of fiber optic cables. It can help us identify breaks, bends or wear of the fiber glass used in single mode or multi-mode optical fiber cables. The light used in optical fiber cables is infrared light so it’s impossible to see where the losses in the cables are happening with the naked eye. This is where VFLs come into the picture as they use light from a powerful laser source which we can use to see where the high losses are taking place in an optical fiber cable.

Fiber Continuity Testers vs. VFLs

The main difference between fiber continuity testers and visual fault locators are the kind of light source they use. Fiber continuity testers use visible LEDs (mainly red or green) whereas visual fault locators use a high power red laser diode (635-670nm). The fiber continuity testers are the more basic ones as they can only help us find out if there is a problem with the fiber by identifying whether light will pass through the entire cable or not. If the light passes through the cables it works well and if not, it requires a more detailed analysis.

Whereas VFLs give us a more detailed analysis by helping us pin-point the exact location the losses are happening because of bad connections or bends, and we don’t have to trouble ourselves with any other equipment for further diagnosis.

The Principle On Which Visual Fault Locators Work

A high power red laser diode is used to send light through the core of the optical fiber cable which can travel for some distance and help us trace the light as it passes through the cables and spot any high losses in them. VFLs have a main application for short distance cables ranging up to a few kilometers and this is why they can be used as a part of OTDRs in regions of OTDR dead zones.

Types of Visual Fault Locators

Visual fault locators come in different shapes and sizes. There are two types based on how they function, namely contact and non-contact. In case of a contact VFL, the optical fiber we are testing comes in direct physical contact with the VFL and in case of a non-contact VFL, the optical fiber we are testing does not come in direct contact with the VFL. For commercial purposes, there are 3 main types of Visual Fault Locators:

Pen-style visual fault locator: This is pocket sized and can be carried around easily. This is a kind of contact VFL.

Hand-held visual fault locator: This is a type of contact VFL and comes in different connector types, ranging from specific connector types to universal.

Portable visual fiber fault locator: This is a non-contact VFL and is used to identify faults and losses in optical fiber cables especially in short range cables like LAN, ATM, FDDI, and telecommunication networks.

Important Parameters of VFLs

Some important parameters by which VFL performance can be measured which are:

Output power- The output power is a very important factor for VFL performance. VFLs can work for longer distances with higher output power.

Fiber distance – This is the maximum distance in the optical fiber cables till which we can see losses or problem areas without much problem. This is determined by the power of the laser diode. Normal VFLs have a 5km range for industrial single mode fibers and 10km range for multi mode fibers.

Wavelength – The wavelength of the VFLs work just fine in the range of 635nm – 670nm.

Modulation frequency – The eye is better able to pick up on a blinking light which is why technicians prefer VFLs with a blinking light rather than a steady one as it helps them diagnose the defects in cables better.

Learned All You Need About Visual Fault Locators?

A Visual Fault locator is an ideal instrument for installation, testing and maintenance of fiber optic cables because it can be used to locate a lot of defects that can occur in optical fiber cables like breaks, cracks, or bends in regions of bad fusion splices. Since the light passing through fiber optic cables is infrared, a visual fault locator is a great tool to help us see the areas which need improvement through our own eyes. A VFL begins its process by emitting light via a powerful red laser through the core of the optical fiber cable. When light passes through the cable, it illuminates the region surrounding the cable(buffer) in regions where there are any anomalies such as breaks, cracks or connector bends, due to radiation of the visible red light. This can work perfectly when used as a part of an OTDR as OTDRs have some blind spots or dead-zones during which we don’t get readings and since VFLs can help us see where our defects are, that solves many problems. Using VFLs can prove to be very useful and boost productivity because it provides quick and easy detection of the damage and helps us find the exact location where the problem lies so technicians can diagnose, troubleshoot and fix the problem in record time.

Polarizing filters are a magical thing! With the advent of digital photography and computerized post-processing, software is now able to recreate many of the effects that creative filters were used for in the past. However, polarizers are one of the few types of filters whose effects cannot be recreated in post-processing. Polarizers change the light coming into the camera and can do some pretty amazing things!

The most common use of polarizing filters is to remove glare from water allowing you not only to see below the surface of the water, but to enhance the overall color of images containing water. But this is far from all that a polarizer can do for you!

Purchasing a polarizing filter:

The first thing you want to make sure of is that you purchase a circular polarizer (sometimes referred to as CPol) if you are just newly stepping into the world of polarizers, as opposed to a linear polarizer. Linear polarizers will cause your in-camera light meter to be unreliable and maybe even unusable. The good news is that circular polarizers are easy to find!

As with most things photography related, you get what you pay for. Polarizers consist of more layers than a typical UV or color filter, and as a result, they are more complicated to manufacture and therefore more expensive than other types of filters. It is important that every layer be of a good quality, otherwise the filter will degrade the quality of the final image. Expect to spend a minimum of $100 on a good quality circular polarizer. (B+W and Heliopan are great brands!)

As with all filters, the size of filter that you buy is based on the filter thread of the lens you are using. However, if you would like to be able to buy just one polarizer and be able to use it on all your lenses, here’s a money-saving trick. Buy your polarizer in the largest filter diameter of all your lenses (or even bigger if lenses with larger filter threads are on your wish list). Then, buy stepping rings so that you can attach the polarizer to your lenses with smaller thread diameters.

I have a 72mm polarizer, but my current lenses have 62mm and 52mm threads. I also have a 72mm to 62mm stepping ring and a 62mm to 52mm stepping ring. I use either one or both of the stepping rings depending on the lens that I am attaching the filter to. Stepping rings cost under $20, so a couple of those are far cheaper than buying a separate polarizer for each lens.

How to use a polarizer:

Start off, of course, by attaching the filter to your lens. While looking through the viewfinder, rotate the outside edge of the PM polarizer. You will see the colors and saturations change as you rotate the filter. When you achieve the desired effect, shoot away! As you rotate the filter through 360°, it will go all the way from minimum effect, to maximum effect, and back to minimum affect TWICE! Or to put it another way, it only takes a 90° rotation to go from minimum effect to maximum effect. Why does this matter? Well, if you’re shooting in landscape orientation and you have rotated your filter for the desired effect and then switch to portrait orientation (rotating the camera 90° in the process), you’re going to completely chance the polarization effect. Every time you change the orientation of you camera, you have to re-adjust your filter.

Polarizers are most effective when shooting at a 90° angle to the sun. So if the sun is directly to your left or right, you are going to see the most dramatic differences as you rotate the filter. If the sun is directly in front of you or directly behind you, you may not see much difference at all.

When to use a polarizer (and when not to use one):

If you want to remove glare from water to take photos of what’s below the surface, this is where a polarizer is really irreplaceable! Here is a photo taken both with and without a polarizer. I promise, there really were dolphins under the surface of the water in both photos, but the glare from the surface of the water meant that without a polarizer I was never going to be able to photograph them.

Polarizers are also great at boosting the overall saturation of an image and can make pretty blue skies even bluer, giving an image with more tonal contrast.

As I mentioned above, polarizers are most effective when shooting at a 90° angle to the sun. This is something that you want to be mindful of when shooting with wide angle lenses. When using a 24mm lens on a full frame camera, you will have an approximately 84° angle of view. This means that one edge of the frame could have the full effect of polarization, while the opposite edge of the frame could have next to nothing. This can result in some pretty crazy and unappealing gradiations in the color of the sky.

Polarizers are like putting sunglasses on your camera. Depending on your exact filter, they can end up giving you 1-2 stops less light. If you are already shooting at the low light limits of your camera, it may be better to forego the polarizing benefits in exchange for the additional light you can get into your camera by removing the polarizing filter.

And one of my favorite little secrets…rainbows have polarized light in them! When shooting a rainbow with a polarizing filter, it will make the colors more vibrant resulting in an almost magical quality that will have you wanting to search for the pot of gold!

If you have never tried shooting with a polarizer before, I’d highly encourage you to give it a try. It can bring a new level to the natural color and contrast of outdoor photos, and it can open up a whole new world of possibilities when taking photos that include water and glass by allowing you to take control of the reflections that you are presented with.

As the data center expands, the traditional fiber optic cables can hardly meet the high requirements for networking, as they not only occupy a large room, but also make it more difficult to manage cables. In contrast, MTP cable and MPO cable provide a multi-fiber connectivity in one connector to support higher bandwidth and higher density applications, thus becoming popular. Generally, MTP/MPO cables are classified into three types: trunk cable, harness cable and conversion cable. See what they are and their applications.

Common MTP/MPO Cable Types

MTP/MPO Trunk Cable

MTP/MPO trunk cable is a cable with two MPO or MTP connectors at both ends, with nothing different from ordinary patch cables seen from outside. However, the truth is that the cable usually accommodates 12, 24, 48 and even 72 fibers, and the ends are terminated with 12-fiber or 24-fiber MTP/MPO connectors according to customer’s choice. fiber-mart.com MTP/MPO trunk cables are designed for high density application which offers excellent benefits in terms on site installation time and space saving. They are available in multiple lengths and in single mode, multimode OM1, OM2, OM3 or OM4 with LSZH or PVC Jackets. With BIF, fiber-mart.com MTP and MPO cables are designed for improved bend performance in reduced-radius applications such as residential or office environments which have less bend sensitivity.

MTP/MPO Harness Cable

MTP/MPO harness cable is also known as fanout cable or breakout cable as it has a single MTP connector on one end and on the other end it breaks out into 6 or 12 connectors (LC, SC, ST, etc.). As one fiber patch cord contains two fibers for receiving and transmitting, a 8-fiber MTP-LC harness cable, for example, has 4 LC connectors and a MTP connector at either end. Similarly, a 12-fiber MTP-LC harness cable has 6 LC connectors and a MTP connector. MTP/MPO harness cable is usually deployed for 40G to 10G transmission and 100G to 25G transmission.

MTP/MPO Conversion Cable

MTP/MPO conversion cable has the same fanout design like the MTP/MPO harness cable, but it is terminated with MTP/MPO connectors on both ends. However, the MTP connectors on each end are different in fiber counts and types, which can provide more possibilities for the existing 24-fiber cabling system. It eliminates the wasted fiber, and therefore can largely increase the capacity of the existing 12-fiber and 24-fiber MTP network.

Conclusion

High performance, high density MTP cable and MPO cable solutions can swap up to 12 traditional fiber connectors with one single small form factor connector, reducing installation time and labor costs. They are suitable for a variety of applications including data centers, telecommunications, broadcast communication, and server rooms. fiber-mart.com strives to provide you with best products with reasonable price and best service.