Optical Time Domain Reflectometer: Three Mistakes you Often Make when Troubleshooting.
Precision in fiber optic measurements serve as a foundation for the seamless networks in the dynamic landscape of fiber optics.
This guide aims to share the knowledge and experience I gained in the field, focusing on the most overlooked tips by fiber technicians.
Readers can therefore enhance their understanding and proficiency in fiber optic technology, ultimately contributing to more efficient and reliable OTDR usage.
1. Opting not to use Launch Cables in Link Testing
One primary reason technicians ignore launch cables is the misconception that direct connections simplify the testing process.
Some technicians perceive launch cables as an additional layer of complexity, assuming that direct connectors offer a straightforward and hassle-free approach to OTDR measurements.
Launch cables facilitate accurate fault identification, particularly near the beginning of the fiber, ensuring precise troubleshooting.
Moreover, their consistent use establishes standardized testing practices, allowing for reliable comparisons over time and scenarios.
By preserving measurement integrity and mitigating initial pulse effects, launch cables become an essential tool, contributing significantly to the precision and reliability of OTDR measurements and, consequently, the overall health and performance of fiber optic networks.
2. Using Connectors for the wrong Purpose
Choosing between Angled Physical Contact (APC) and Ultra Physical Contact (UPC) connectors for OTDR testing depends on the specific requirements of the optical network and the desired outcome of the measurements.
Each connector type offers distinct advantages in particular scenarios, influencing factors such as back reflections, network distance, and the nature of the optical system.
For APC connectors, the typical range of back reflection is around -60 dB to -70 dB. This is due to the angled endface of APC connectors, which minimizes the direct reflection of light back into the optical source.
For UPC connectors, the backreflection value is also specified in terms of Return Loss (RL) or reflectance. The reflectance level for UPC connectors typically falls within the range of -50 dB to -55 dB.
In the context of OTDR measurements, where accuracy is paramount, the lower backreflection provided by APC connectors makes them preferable in scenarios where minimizing signal degradation due to reflections is critical.
This is particularly important in long-haul networks, wavelength-sensitive systems like DWDM and CWDM, and deployments where precise signal integrity is essential.
While UPC connectors may be suitable for applications with shorter distances and less stringent reflectance requirements, APC connectors are the preferred choice for optimizing the precision of OTDR measurements in environments where back reflections can significantly impact signal quality.
SC: Quick push-and-pull fitting. It is compact, allowing a big density of connectors per instrument. It is used in FTTH, telephony, CATV, etc. Best for single mode and multimode fibers. Losses of 0.25 dB.
NOTE: a typical FTTH pigtail with an SC/APC connector is referring to an SC connector with an APC polishing.
3. Cleaning OTDR Terminals and Connectors
https://youtu.be/7_PrhlrKc6o?si=gOzGEJWjfRJMEU60
Most technicians assume that cleaning optical fiber connectors is a straightforward task, often overlooked in the haste of deploying or troubleshooting networks.
However, the cleanliness of connectors plays a pivotal role in maintaining signal integrity and ensuring accurate measurements, particularly when using an OTDR.
Contrary to common belief, a cursory visual inspection is not sufficient, and a systematic cleaning procedure with the right products is imperative for optimal OTDR performance.
To clean OTDR terminals effectively, technicians should follow a systematic approach and use specialized cleaning products.
- Inspect Connectors: Before cleaning, visually inspect the connectors and terminals for any visible dirt, dust, or damage. This initial inspection helps identify the extent of cleaning required.
- Use Compressed Air: Blow away loose particles using compressed air. This step helps remove large particles that may scratch the connector during the cleaning process.
- Apply Cleaning Solution: Use a high-quality optical fiber cleaning solution specifically designed for connectors. Apply the solution to a lint-free cleaning cloth or cleaning swab. Avoid using cotton swabs or tissues, as they may leave lint residue.
- Clean the Connectors: Gently wipe the connectors in a circular motion, ensuring thorough cleaning. Be cautious not to touch the cleaned surfaces with bare fingers to prevent recontamination.
5. Inspect Again: After cleaning, inspect the connectors once more to verify that all contaminants have been effectively removed. Repeat the process if necessary.
Recommended Cleaning Products:
- Isopropyl Alcohol Wipes: Isopropyl alcohol wipes are effective for removing contaminants and ensuring a clean, dry surface. Choose wipes with a high alcohol concentration for optimal cleaning.
2. Optical Fiber Cleaning Solutions: Specialized optical fiber cleaning solutions, available in spray or liquid form, are designed to dissolve and remove oils and other stubborn contaminants. These solutions are safe for use on optical connectors.
3. Cleaning Swabs and Sticks: Lint-free cleaning swabs or sticks are suitable for applying cleaning solutions to connectors. Ensure they are designed for optical fiber cleaning to prevent any potential damage.
4. One-Click Cleaners: One-click cleaners are convenient and efficient tools designed for cleaning connectors with a simple push-button operation. These devices typically contain a cleaning tape that removes contaminants with each click.
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I thank Fiber Instruments Sales and Fluke Networks and other networking bodies for the roles they’re playing in the networking realm.
Thank you for reading !
