How to operate an OTDR?

An optical time-domain reflectometer (OTDR) is an essential tool for testing and troubleshooting fibre optic cables. It is used to measure the attenuation and reflectance of light signals traveling along the length of the fibre, helping to identify any faults or damages that may occur. In this article, we will discuss how to operate an OTDR and explore its various features.

Understanding the OTDR

An OTDR operates by sending a short pulse of light into a fibre optic cable and then measuring the light that is reflected back to the source. This reflected light, or backscatter, provides information about the attenuation and reflectance of the cable.

The OTDR calculates the distance to any faults or discontinuities by measuring the time it takes for the pulse to travel through the cable and return to the source.

Using an OTDR requires a basic understanding of fibre optic technology and terminology. For instance, the terms “backscatter,” “attenuation,” and “reflectance” are fundamental concepts in fibre optic testing. Furthermore, you should be familiar with the different types of fibre optic cables, connectors, and splices.

Preparing to Operate an OTDR for Testing

Before beginning the testing process, there are several preparatory steps that you should follow:

• Ensure that you have the appropriate test equipment, including the OTDR, test cables, and connectors.
• Clean the fibre optic connectors using a specialized cleaning kit to ensure that there is no dirt, oil, or debris on the connectors. Dirty connectors can cause inaccurate measurements and affect the performance of the OTDR.
• Familiarize yourself with the OTDR user manual and make sure you understand its various features and capabilities.
• Set up the OTDR by connecting it to the fibre optic cable that you wish to test. You can use either a launch cable or a receive cable to connect the OTDR to the cable.
• Turn on the OTDR and set the testing parameters, such as the wavelength, pulse width, and averaging time.

OTDR Testing Procedure

After completing the preparatory steps, you can now begin testing the fibre optic cable using the OTDR. The following steps outline the OTDR testing procedure:

Step 1: Configure the OTDR

The first step is to configure the OTDR settings to match the fibre optic cable you wish to test. This includes selecting the appropriate wavelength, pulse width, and averaging time. The wavelength should match the type of fibre optic cable you are testing (e.g., single-mode or multi-mode).

The pulse width and averaging time should be set based on the length of the cable and the level of detail required.

Step 2: Set up the test cable

Connect the test cable to the OTDR and the fibre optic cable to be tested. A launch cable can be used to ensure accurate measurement of the fibre optic cable’s characteristics. A receive cable can also be used to measure the reflected light from the end of the cable.

Step 3: Begin the OTDR test

Start the OTDR test and wait for the measurement to complete. The OTDR will display a trace of the light signal that has been sent and received by the cable. The trace will show any losses or changes in the signal strength as it travels through the fibre optic cable. You can then use this trace to identify any faults or problems in the cable.

Step 4: Analyze the results

Once the test is complete, you can analyze the results and interpret the OTDR trace. Look for any changes in the signal strength, such as dips or spikes, that indicate a problem with the cable. The OTDR trace can help you identify the location of the problem, whether it is a break in the cable or a faulty connector.

Step 5: Repeat the test

If you identify a problem with the cable, you should repeat the OTDR test to confirm the location and extent of the problem. Make any necessary adjustments to the testing parameters, such as the wavelength or pulse width, to ensure accurate measurements.

Advanced OTDR Features

In addition to its basic functions, the OTDR also offers several advanced features that can help you to perform more detailed testing and troubleshooting.

• Live Fibre Testing: This feature allows you to test an active fibre optic cable while it is in use. You can use this feature to monitor the performance of a fibre optic network or to identify any issues with an active cable.
• Multi-wavelength Testing: Multi-wavelength testing allows you to test a fibre optic cable at multiple wavelengths simultaneously. This can provide a more detailed analysis of the cable’s performance and identify any issues that may not be visible at a single wavelength.
• Automated Analysis: Some OTDRs offer automated analysis tools that can help you to quickly and easily identify issues with the cable. These tools can analyze the OTDR trace and provide a detailed report on the cable’s performance.
• Data Storage and Reporting: OTDRs often come with software that allows you to store and analyze OTDR traces. This can help you to track changes in the cable’s performance over time and identify any recurring issues.

Conclusion

Operating an OTDR is a crucial skill for any fibre optic technician. By following the proper procedures and using the appropriate testing parameters, you can identify and troubleshoot any issues with fibre optic cables.

The advanced features of the OTDR can also help you to perform more detailed testing and analysis. With proper training and experience, you can become proficient in operating an OTDR and ensure the optimal performance of fibre optic networks.

FAQs:

What is the difference between a launch cable and a receive cable?
A launch cable is used to ensure accurate measurements of the fibre optic cable’s characteristics by eliminating any dead zone at the beginning of the cable. A receive cable is used to measure the reflected light from the end of the cable.

How do I clean fibre optic connectors?
You can use a specialized cleaning kit to clean fibre optic connectors. Make sure to remove any dirt, oil, or debris from the connectors to ensure accurate measurements.

What parameters do I need to set on the OTDR?
You need to set the appropriate wavelength, pulse width, and averaging time based on the type of fibre optic cable and the length of the cable you are testing.

What is live fibre testing?
Live fibre testing is a feature that allows you to test an active fibre optic cable while it is in use. This can help you to monitor the performance of the cable and identify any issues that may arise.

What is multi-wavelength testing?
Multi-wavelength testing allows you to test a fibre optic cable at multiple wavelengths simultaneously. This can provide a more detailed analysis of the cable’s performance and identify any issues that may not be visible at a single wavelength.