Fiber Optic Network Fault Testing Equipment Analysis

In recent years, as people's requirements for broadband speed have become increasingly higher, optical fiber has been widely used in the backbone construction of broadband projects due to its superior performance compared to copper cables. Meanwhile, as the coverage of optical fiber continues to expand, the detection of fiber faults has become increasingly important. What methods can be used to troubleshoot fiber component failures? First, troubleshooting fiber component failures certainly requires testing. So what testing and measurement equipment is available for fiber optic networks? Currently, according to the Cat6A cable manufacturer VCOM, there are mainly three types of instruments: optical loss testing equipment (also known as optical multimeter or optical power meter), fault locator (fault tracer), and fiber identifier.

1. Optical Loss Testing Equipment (composed of an optical multimeter and an optical power meter)

Optical power meter: used to measure absolute optical power or the relative loss of optical power transmitted through a section of optical fiber. Optical multimeter: used to measure the optical power loss of a fiber optic link.

To measure the loss of a fiber optic cable link, calibrated stable light needs to be launched at one end, and the output power is read at the receiving end. These two devices together constitute an optical loss tester. When the light source and power meter are combined into a single instrument, it is often referred to as an optical loss tester (also called an optical multimeter by some). When measuring the loss of a link, one person is required to operate the test light source at the transmitting end while another person measures with an optical power meter at the receiving end, which only yields a loss value in one direction.

Typically, we need to measure the loss in both directions (due to directional connection loss or the asymmetry of cable transmission loss). In this case, technicians must exchange equipment and perform measurements in the other direction. But what should they do when they are separated by more than ten floors or dozens of kilometers? Obviously, if each of the two people has both a light source and an optical power meter, they can measure simultaneously at both ends. Current advanced fiber optic cable test kits used for certification testing can support bidirectional dual-wavelength testing, such as Fluke's CertiFiber and the FTA fiber optic test kit of the DSP cable test series.

2. Fiber Optic Fault Locator (Fault Tracer)

Fault locators are mostly handheld instruments suitable for both multimode and single-mode fiber optic systems. Using OTDR (Optical Time Domain Reflectometer) technology, they are used to locate the position of fiber faults, with test distances mostly within 20 kilometers. The instrument directly displays the distance to the fault point digitally. It is suitable for: WAN (Wide Area Network), communication systems within a 20 km range, Fiber to the Curb (FTTC), installation and maintenance of single-mode and multimode fiber optic cables, as well as military systems. In single-mode and multimode fiber optic cable systems, the fault locator is an excellent tool for locating faulty connectors and bad splice points. The fault locator is simple to operate, requiring only a single-button operation, and can detect up to 7 multiple events.

This device is based on a laser diode visible light (red light) source. When light is injected into the fiber, if faults such as fiber breaks, connector failures, excessive bending, or poor splice quality occur, the light launched into the fiber can be used for visual fault location. The visual fault locator emits in continuous wave (CW) or pulse mode. The typical frequency is 1 Hz or 2 Hz, but it can also operate in the kHz range. The typical output power is 0 dBm (1 mW) or less, with an operating distance of 2 to 5 km, and it supports all common connectors.

3. Fiber Identifier

It is a highly sensitive photoelectric detector. When you bend an optical fiber, some light radiates out from the core. This light can be detected by the fiber identifier, allowing technicians to identify a single fiber from among others in a multi-fiber cable or patch panel. The fiber identifier can detect the status and direction of light without affecting transmission. To make this task easier, a test signal is typically modulated at 270 Hz, 1000 Hz, or 2000 Hz at the transmitting end and injected into a specific fiber. Most fiber identifiers are used for single-mode fiber optic cables operating at wavelengths of 1310 nm or 1550 nm. The best fiber identifiers can utilize macro-bending technology to identify cables online and test the transmission direction and power in the cable.

In summary, projects that extensively use fiber optic equipment are generally large-scale engineering undertakings. To complete an optical loss measurement task or troubleshoot fiber equipment faults, a calibrated light source and a standard optical power meter are indispensable.