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The AE3100's high-performing OTDR supports up to 3 wavelengths and is the ideal solution for testing the fiber in RFoG and FTTx applications. The OTDR can identify and locate link impairments and measure the insertion loss by LSA, 2Pt and 4Pt methods. The unit also measures optical return loss (ORL).
Display
Deviser AE3100 OTDR comes with LCD Touch Screen Display. With Minimum of 5 cm resolution display.
Lowest Event and Attenuation Deadzone
Excellent short-distance performance with 0.8m event deadzone and 4m attenuation deadzone
FiberPath™
FiberPath simplifies OTDR trace interpretation by IDing reflective events and mapping them in an easy-to-understand format. Experienced and inexperienced technicians alike will appreciate the simplified display.
FiberPath's Auto Test automatically runs many tests at different wavelengths and pulse widths.
Remote Control
In conjunction with the SYNCOR PC-based asset and test data management system, users can issue test orders and collect measurement data remotely from AE3100 units deployed to the field.
Versatility
Multiple options for your measurement needs, including: VFL, power meter, light source, and optical fiber microscope
Optical Measurements
The Fiber optic otdr Testing AE3100 includes a suite of optical measurement tools, including a power meter, laser source, and visual fault locator (shown below). The unit is available in numerous wavelength configurations for ensuring proper levels in networks such as RFoG and FTTx.
Search here the OTDR for Fiber Optic Network in Major cities i.e Delhi, Hyderabad, Chennai, Ahmedabad, Bangalore, Jammu & Kashmir, Patna, Kolkata, Lucknow & More. Candid Optronix is one of the biggest authorized & Certified distributors, importers & Suppliers of Deviser OTDR in India.
We have various types of Optical time domain Reflectometer AE Series. To Know OTDR AE Series Specification, please watch this Video Here -
Key Features:
A 7" touch screen provides a more convenient user interface and professional user experience.
A 0.8m event dead zone and 4m attenuations dead zone provide excellent short-distance performance.
Excellent dynamic range coverage supporting 28-45 dB dynamic range.
Min 5cm resolution.
Intelligent analysis of events
Excellent stability and repeatability.
Multiple options, supporting different measurement plans; VFL, Power meter, light source, optical fiber microscope, and QAM analysis module.
Complete user data ports; support LAN, USB, SD and etc.
Today fiber networks are the lifeblood of high-speed networking for virtually all applications. Fiber-optic technology to reach the fastest speeds available today, as fast as 10000 Mbps (1Gpbs). For most of us, what happens behind the scenes to turn them up and keep them operating efficiently is unseen. But for technicians, engineers, and others in the industry who live it every day, keeping networks up and running is a constant challenge. Higher we push network speeds and resulting complexities, the more challenging it becomes.
If I talk about earlier slower speed network could tolerate issues with little or no impact but With higher speeds comes increased sensitivity to more factors in the network. But while continuous upgrades in technology have resulted in more dynamic and adapting networks today, the fundamental requirements for fiber performance remains mostly unchanged.
Establishing and maintaining networks requires accurate testing of the fiber infrastructure to ensure it can handle the system’s performance requirements and keep it operational. There is a wide range of tools that can accomplish these tasks, but there is arguably no other single instrument more important for testing and maintaining fiber networks than the Optical Time Domain Reflectometer (OTDR).
Determining the Health of Your Network
The OTDR has been around since the first fiber was installed and became commercially operational in the early 1980s. Today it is still the only optical test device that provides a visual view of the fiber link, providing a “fingerprint” of each fiber strand.
The information an OTDR provides is vast, including distance details from one end of the fiber to the other, performance of events in between and for the link overall. The information gained by testing with an
OTDR is effectively equivalent to creating a health certificate for the specific fiber link tested. (See Figure 1.)
A properly configured OTDR operated by an experienced technician can capture the following important fiber network data:
Length of the fiber link (meters, km, feet, or miles).
2. Distance between spans and to events in the link (splices, connectors).
3. Loss of connector interfaces and splices (dB).
4. Loss of fiber sections between splices as a function of length (dB/km).
5. Losses due to excess fiber bending (dB — varies w/ wavelength).
6. Link Optical Return Loss (ORL) in dB.
7. Optical Reflectance of each reflective event in the link (-dB).
In the preceding list of measurements, link loss and ORL are often officially documented using other traditional loss measurement methods. While OTDRs provide the same measurements using a different test method, the added benefit of using both methods is to establish a cross-correlation of test data. Since link loss and ORL performance are so important, cross-checking data results help ensure tests are performed correctly and the resulting data is valid.
In addition to cross-checking results, OTDRs have an added value of enabling identification of mismatches between connected fibers. These occur commonly when multiple reels are spliced together. Mismatches can be due to splicing or connecting old to new, between different fiber manufacturers, or between different fiber types (e.g., G.652 to G.655).
Given the wide range of test data provided by the OTDR, its value should not be underestimated. As with most comprehensive tools, purchasing an OTDR Machine is a substantial investment; and to get the most value for your money it is important to understand how to properly set up and operate the device.
Questions to Ask Before Purchasing
There are basic but critical questions important to answer before making a purchase to make sure you are buying one that meets your needs.
1. Are you using an OTDR that matches well with your applications?
2. Is your link single-mode or multimode?
3. Based on your operating wavelengths, which wavelengths should be tested?
4. How much dynamic range is needed to optimally test your fibers?
Hopefully these considerations were included during the OTDR selection and purchase process, although sometimes companies realize later that they purchased testers that were not ideally suited for their applications. That issue goes beyond the scope of this article, so we will save that topic for another time.
For this series, we will assume you have purchased the OTDR in the configuration(s) that meet your requirements. But making the right purchase is just the beginning of getting the most out of the instrument. Too many users, even experienced ones, do not realize that if the OTDR is not
setup or configured correctly for their specific parameters, then the data the fiber optic tester provides can be compromised, resulting in limited or even inaccurate results. combination of knowledge and proper setup is key to accurately assessing links to ensure optimum operation.
Real World Examples: Don’t Let This Happen to You
An OTDR properly configured for the correct testing application and used by an experienced operator is an indispensable tool. But like any other tool, if an OTDR is not properly setup for the application being tested, the results can be misleading or inaccurate.
First let’s look at some real-world scenarios where the OTDR was not optimized and therefore failed to provide the needed information.
Scenario #1: OTDR to Link Connectivity
Example: Low power launch / High reflectance
A technician has completed acceptance testing on a pair of fibers in the field. He submits a report with an OTDR trace showing high span loss (dB/km) in the initial section of the fiber and a noisy trace near the fiber end. There is also high reflectance contributing to a large dead zone which masks most of the data from the first fiber section. The result is a poor launch (low power) which also reduces the dynamic range.
Figure 2. A poor trace.
These issues translate the following to the OTDR trace:
1. The higher reflectance at the start means we cannot clearly see the near-end patch panel, and therefore we cannot measure the loss performance of that connection.
2. The high loss at the front end can also impact the trace downstream, causing it to be noisier. In especially longer links, we might be unable to display a clean, smooth trace; or we might have to use a longer pulse width to overcome the noise, which lessens our event clarity.
A technician shooting between 2 data centers submits traces showing links that appear fine at the time, but engineers reviewing the trace data later see the mid-span (where the trouble is suspected) with one wide reflection and >1dB loss. Engineers are aware of a patch through with about 150m of fiber in-between patches, but they are unable to view the 2 patch interfaces individually.
In this example, the trace might appear normal at first look or to the untrained eye. But to a skilled OTDR user, and based on the trace view and OTDR settings, a shorter pulse width could potentially separate and measure each of the mid-span panels. (See Figure 3.)
Four test teams are conducting bi-directional testing for multiple span acceptance tests. (Bi- directional means data in both directions are averaged to get the true loss data for the link.) However, management set tight work timelines to minimize testing time per job by each technician, so OTDR setups prior to testing at each span were rushed, and not all settings were checked.
Later, when engineers attempted to load the stored results during post-testing, the A>B and B>A directional data files would not line up properly with each other. File names did not match, and pulse widths and display ranges were inconsistent. This resulted in bi-directional documentation being fragmented, inconsistent, and difficult to analyze. These issues required time-consuming manual file edits to be performed to enable traces to be processed correctly. Reported results were also inconsistent due to variations in pulse widths and display ranges between test traces.
Avoiding OTDR Issues
The problems in scenarios like those noted above could have been minimized or potentially avoided all-together IF best practices were implemented and proper training and reasonable time allotments were enabled for test technicians. These practices would help to ensure correct and optimized setups and naming is implemented and validated consistently.
While the OTDR is a powerful and flexible tool, its effectiveness depends on the user’s ability and opportunity to set it up and use it properly. This series of fiber network articles will highlight the most critical aspects of OTDR operation and data collection, and it will explain how trained and savvy users can get the most from OTDR results. We will also examine problem scenarios like those introduced earlier in more detail, and explain how to avoid them.
Coming Up Next
Stay tuned for our next installment: “OTDR to Link Connectivity” — the first step in effective testing. We will explore why good connectivity is so important. We’ll look at how good connectivity and poor connectivity differ visually and the most common reasons for each. And we will share best practices on how to optimize connectivity when using an OTDR and how this helps to get the best testing results.
Unlike sources and power meters which measure the loss of the fiber optic cable plant directly, the OTDR works indirectly. The source and meter duplicate the transmitter and receiver of the fiber optic transmission link, so the measurement correlates well with actual system loss. The OTDR, however, uses a unique optical phenomenon of fiber to indirectly measure loss.
The biggest factor in optical fiber loss is scattering. In fiber, light is scattered in all directions, including some scattered back toward the source as shown here. The OTDR uses this "backscattered light" to make measurements along with reflected light from connectors or cleaved fiber ends.
The OTDR consists of a high power laser transmitter that sends a pulse of light down the fiber. Back-scattered light and reflected light returns to the OTDR through the fiber and is directed to a sensitive receiver through a coupler in the OTDR front end. For each measurement, the OTDR sends out a very high power pulse and measures the light coming back over time. At any point in time, the light the OTDR sees is the light scattered from the pulse passing through a region of the fiber. Think of the OTDR pulse as being a "virtual source" created by the scattering that is testing all the fiber between itself and the OTDR as it moves down the fiber. Since it is possible to calibrate the speed of the pulse as it passes down the fiber from the index of refraction of the glass in the core of the fiber, the OTDR can correlate what it sees in backscattered light with an actual location in the fiber. Thus it can create a display of the amount of backscattered light at any point in the fiber along its length.
There are some calculations involved. Remember the light has to go out and come back, so you have to factor that into the time calculations, cutting the time in half. One must also cut the loss in half since the light sees loss both ways. The power loss is a logarithmic function, so the power is measured and displayed in dB.
The amount of light scattered back to the OTDR is proportional to the backscatter of the fiber, peak power of the OTDR test pulse and the length of the pulse sent out. If you need more backscattered light to get good measurements, you can increase the pulse peak power or pulse width or send out more pulses and average the returned signals. All three are used in many OTDRs, with user control of some of the selections.
OTDRs are always used with a launch cable and may use a receive cable. The launch cable, sometimes also called a "pulse suppressor," allows the OTDR to settle down after the test pulse is sent into the fiber and provides a reference connector for the first connector on the cable under test to determine its loss. A receive cable may be used on the far end to allow measurements of the connector on the end of the cable under test also.
Information in the OTDR Trace
They say a picture is worth a thousand words, and the OTDR picture (or "trace" as they are called) takes a lot of words to describe all the information in it! Consider the diagram of a trace at the right.
The slope of the fiber trace shows the attenuation coefficient of the fiber and is calibrated in dB/km by the OTDR. In order to measure fiber attenuation, you need a fairly long length of fiber with no distortions on either end from the OTDR resolution or overloading due to large reflections. If the fiber looks nonlinear at either end, especially near a reflective event like a connector, avoid that section when measuring loss.
Connectors and splices are called "events" in OTDR jargon. Both should show a loss, but connectors and mechanical splices will also show a reflective peak. The height of that peak will indicate the amount of reflection at the event unless it is so large that it saturates the OTDR receiver. Then peak will have a flat top and tail on the far end, indicating the receiver was overloaded.
Sometimes, the loss of a good fusion splice will be too small to be seen by the fiber testing OTDR. That's good for the system but can be confusing to the operator. It is very important to know the lengths of all fibers in the network, so you know where to look for events and won't get confused when unusual events show up (like ghosts, we'll describe below.)
Reflective pulses can show you the resolution of the OTDR. You cannot see two events closer than is allowed by the pulse width. Generally, longer pulse widths are used to be able to see farther along the cable plant and narrower pulses are used when high resolution is needed, although it limits the distance the OTDR can see.
Making Measurements With The OTDR
Fiber Attenuation by Two Point Method.
The OTDR measures distance and loss between the two markers. This can be used for measuring the loss of a length of the fiber, where the OTDR will calculate the attenuation coefficient of the fiber or the loss of a connector or splice.
To measure the length and attenuation of the fiber, we place the markers on either end of the section of fiber we wish to measure. The OTDR will calculate the distance difference between the two markers and give the distance. It will also read the difference between the power levels of the two points where the markers cross the trace and calculate the loss or difference in the two power levels in dB. Finally, it will calculate the attenuation coefficient of the fiber by dividing loss by distance and present the result in dB/km, the normal units for attenuation.
In order to get a good measurement, it is necessary to find a relatively long section of fiber to give a good baseline for the measurement. Short distances will mean small amounts of loss, and the uncertainty of the measurement will be higher than if the distance is longer. It is also advisable to stay away from events like splices or connectors, as the OTDR may have some settling time after these events, especially if they are reflective, causing the trace to have nonlinearities caused by the instrument itself.
Fiber Attenuation by Least Squares Method
The OTDR measures distance and loss between the two markers but calculates the best fit line between the two points mathematically using the "least squares" method to reduce noise. When the markers are selecting the noisy part of the fiber trace, the least squares attenuation (2-pt LSA) tool can be applied to calculate the dB loss between the cursors. Look closely and you will see a thick grey line between the markers, indicating the best fit to the trace, averaging all the noise.
Splice Loss by Two Point Method
The OTDR measures distance to the event and loss at an event - a connector or splice - between the two markers.
To measure splice loss, move the two markers close to the splice to be measured, having each about the same distance from the center of the splice. The splice won’t look as neat as this, with the instrument resolution and noise making the traceless sharp looking, as you will see later on. The OTDR will calculate the dB loss between the two markers, giving you a loss reading in dB.
Measurements of connector loss or splices with some reflectance will look very similar, except you will see a peek at the connector, caused by the back reflection of the connector.
Splice Loss by Least Squares (LSA)
The OTDR measures distance and loss at an event - a connector or splice - between the two markers but calculates the best fit line between the two points using the "least squares" method to reduce noise.
If you noticed, the markers are separated by some distance, which includes the loss of some fiber on either side of the actual connector or splice Most OTDRs will calculate the loss for you by extrapolating the fiber traces on both sides of the event and calculating the loss without any influence from the fiber length. The mathematical method uses is called "Least Squares Approximation", hence the term "LSA" used by many OTDRs in their display and setup menus. Setting LSA requires setting several markers - one on the peak, the two regular markers near the event and the two end markers which define the segments used for least-squares analysis. These segments should be long enough to allow good measurement but not so long as to approach other events.
Reflectance
The OTDR measures the amount of light that's returned from both backscatter in the fiber and reflected from a connector or splice. The amount of light reflected is determined by the differences in the index of refraction of the two fibers joined a function of the composition of the glass in the fiber, or any air in the gap between the fibers, common with terminations and mechanical splices.
This is a complicated process involving the baseline of the OTDR, backscatter level and power in the reflected peak. Like all backscatter measurements, it has a fairly high measurement uncertainty but has the advantage of showing where reflective events are located so they can be corrected if necessary.
By choosing the reflectance measurement and putting the right (blue) cursor on the peak of the reflection and the left (red) cursor just to the left of the reflection, the OTDR will measure the reflectance.
Comparing Traces
Comparing two traces in the same window is useful for confirming data collection and contrasting different test methods on the same fiber. Comparisons are also used to compare fiber traces during troubleshooting with traces take just after installation to see what has changed. All OTDRs offer this feature, where you can copy one trace and paste it on another to compare them. Here is an example of how you can use this feature.
Note that the two traces are taken from the same multimode fiber cable plant at different test wavelengths. The major difference in the slope of the traces displays the different attenuation coefficient of the fiber. The blue line (top) represents the attenuation coefficient of the cable in at 1300 nm, the green line (bottom) represents the same cable measured at 850 nm. There is also a noticeable difference in the reflectance at the splice. Variations in reflectance due to the wavelength difference is not unusual.
Other reasons you might want to compare two traces includes:
Compare several fibers in the same cable to see if they are different.
Traces taken at different times to see if the cable has changed.
At different wavelengths, since fiber is more sensitive to stress at longer wavelengths, this allows finding stress points caused by installation.
At different pulse widths (below) to decide which setting gives the best compromise between noise and resolution or to find events lost with wide pulse widths.
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