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The OTDR: The tool operators are missing out on

Currently, cable-based telecommunications is synonymous with optical fiber. Key carriers in various countries globally, for example in Spain, have either ceased support for traditional telephone access lines or are in the midst of the process. Consequently, fiber has established itself as the mainstay of data networks. This is the moment for all technical staff to upskill.

We entered 2025 fully prepared: Due to optical fiber having been developed for decades, the associated equipment is extremely mature and straightforward to operate.

Time and again, after discussions with professionals, we are astonished to find out how many are still missing out on the benefits of an OTDR (Optical Time Domain Reflectometer) in their equipment, simply because they are unaware of what an OTDR is and its purpose. Join us in this short article and discover the benefits this handy tool provides.

What is an OTDR, and what is its application?

How can the physical location of a break or any other issue be pinpointed in a fiber optic network that may span several kilometers?

The most efficient way to physically locate the event causing the problem is to use an OTDR.

Working with optical fiber is easy

Beyond these faults, the OTDR can physically locate other issues such as macrobends and attenuations originating from a poorly executed connection. Ultimately, we can characterize the optical fiber network to perform troubleshooting tasks and, very importantly, execute proper preventive maintenance.

An OTDR is a device that sends laser light pulses down a fiber optic cable. The light travels the length of the cable and is reflected back at every event, like splices, connectors, and breaks. The OTDR measures how long the light takes to return and the strength of that reflected signal. This data is used to generate a chart that shows the cable's total length, where the events are located, and the power loss at each spot.

Using an OTDR is the most efficient method for pinpointing a fiber optic cable fault.

OTDRs aren't luxury tools anymore

Previously, OTDRs were prohibitively expensive instruments that were only within reach of major telecom carriers.

That meant technicians couldn't use these tools to troubleshoot issues in smaller, local networks. They had to resort to finding problems using simple, low-tech methods—mixing light sources, power meters, and a whole lot of patience and clever thinking.

PROMAX offers OTDRs for under €900

With the launch of PROMAX microOTDRs, optical reflectometers are no longer luxury equipment. The PROLITE-44 and PROLITE-45 are within the reach of any operator, no matter how small. And they offer more than sufficient features to determine network problems at distances up to 120 Km.

The PROLITE-44 are ultra-compact OTDRs that fit in every pocket... and every wallet. They locate faults up to 120 km and include a Visual Fault Locator (VFL), a selective power meter, and a high-capacity battery that charges via USB and ensures hours of work.

The OTDR is the fiber optic multimeter

Thanks to these instruments becoming more affordable, the OTDR is the must-have tool in the case of every fiber network installation and maintenance team:

• Measurement of partial or total attenuation across a fiber optic span: This capability is critical for assessing fiber quality and mitigating potential bottlenecks or connectivity issues. It is an OTDR's main function.
• Identification and localization of loss and reflectivity events: An OTDR can detect and accurately locate attenuation events within a fiber optic link, including splices, connectors, and fractures. The device indicates the physical distance to each loss event and the magnitude of the loss at that location.
• Measuring the length of a fiber optic link: You can use an OTDR to measure the exact distance of a fiber optic run.
• Fiber optic link characterization: An OTDR delivers data on the link's properties, such as the fiber type, attenuation, and dispersion.
• Troubleshooting fiber optic link failures: An OTDR is essential for diagnosing a broad spectrum of fiber optic link failures, such as breaks, faulty splices, and excessive attenuation.

The units also come with a power meter and a VFL (Visual Fault Locator) to complement the OTDR function and allow for a preliminary inspection.

Graphic representation of an optical fiber line analyzed using an OTDR. By looking into the events it is possible to discover fusion splices, connectors, splitters or macrobend and it is possible to physically locate the point of the network there these events are taking place.

Launch cables are a must-have for any OTDR job

You can’t detect fiber faults right at the beginning of the test; the OTDR has a minimum operating distance. Any event within this short section—called the “dead zone”—will either not show up or give you poor readings.

To bypass the dead zone and ensure you catch events close to the test starting point, you need to use a launch cable.

Launch cables (or launch fibers) are comprised of a known length of fiber optic cable, which is connected between the OTDR and the fiber span undergoing testing. This setup ensures that the OTDR's blind spot, or dead zone, is isolated within the launch cable itself. Consequently, the OTDR can clearly detect and analyze every event right from the true start point of the fiber optic link.

These reels offer precise, specified attenuation per kilometer to guarantee measurement accuracy, and they come in various lengths to suit different requirements. PROMAX offers singlemode versions in 150m and 1000m lengths, alongside multimode reels in 150m, catering to the complete line of OTDRs available in our catalog.

PROMAX is a leading manufacturer of test and measurement systems, broadcast and TV signal distribution equipment. Our product lines include measuring instruments for cable TV, satellite TV, broadcast, wireless and fibre optics networks, FTTH and GPON analyzers. DVB-T modulators, IP streamers or IP converters (ASI, DVB-T) are among the company’s latest developments.