Brief introduction of ADSS optical fiber cable test parameters and test methods
 
After the ADSS cable is installed, the link transmission characteristics need to be tested. The most important test items are the attenuation characteristics of the link, the insertion loss of the connector, and the return loss. Below we will briefly introduce the measurement of key physical parameters of ADSS cable routing and troubleshooting and maintenance in the network.

1.1. Key physical parameters of the fiber link

A. Attenuation:
a) Attenuation is the reduction in optical power of light as it travels along the fiber.
b) Calculation of the total attenuation of the ADSS cable network: Fiber Loss (LOSS) is the ratio of the power out of the fiber output to the power in when it is transmitted to the fiber.
c) The loss is proportional to the length of the fiber, so the total attenuation not only indicates the fiber loss itself, but also the length of the fiber.
d) Fiber loss factor (α): To reflect the characteristics of fiber attenuation, we introduce the concept of fiber loss factor.
e) Measurement of attenuation: Since the fiber is connected to the source and the optical power timing inevitably introduces additional losses. Therefore, in the field test, the test reference point setting (ie, the setting of zeroing) must be performed first. There are several methods for testing the reference point, mainly based on the tested link object. In the fiber cabling system, since the length of the fiber itself is usually not long, the test method will pay more attention to the connection. The method and the test jumper, the method is more important.
B. return loss: reflection loss, also known as return loss, refers to the number of decibels of the ratio of retroreflected light to input light at the fiber connection. The larger the return loss, the better, to reduce the reflected light to the source. And the impact of the system. The method of improving the return loss is to use an optical fiber end face as a spherical or oblique spherical surface as an effective method to improve the return loss.
C. Insertion Loss: Insertion loss is the number of decibels of the ratio of the output optical power to the input optical power after the optical signal in the fiber passes through the active connector. The smaller the insertion loss, the better. The insertion loss is measured in the same way as the attenuation.
 
1.2 Test and measurement equipment for ADSS cable network

A. fiber recognizer
It is a very sensitive photodetector. When you bend a fiber, some of the light is radiated from the core. The light is detected by the fiber identifier, and the technician can identify the single fiber in the multi-core fiber or the patch board from the other fibers based on the light. The fiber identifier can detect the state and direction of light without affecting transmission. In order to make this work easier, the test signal is usually modulated at the transmitting end to 270 Hz, 1000 Hz or 2000 Hz and injected into a specific fiber. Most fiber discriminators are used for single mode fiber optics with a working wavelength of 1310 nm or 1550 nm. The best fiber discriminators are the ability to identify the direction and power of transmission in the fiber and test fiber online using macrobend technology.
B. fault locator (fault tracker)
This device is based on the laser diode visible light (red light) source. When light is injected into the fiber, if there is a fiber failure, connector failure, excessive bending, poor welding quality, etc., the light emitted through the fiber can be on the fiber. The fault is visually located. The visual fault locator is transmitted in continuous wave (CW) or pulsed mode. Typical frequencies are 1 Hz or 2 Hz, but can also operate in the kHz range. Typical output power is 0dBm (1Mw) or less, working distance is 2 to 5km, and supports all common connectors.
C. optical loss test equipment (also known as optical multimeter or optical power meter)
In order to measure the loss of a fiber link, it is necessary to emit calibrated steady light at one end and read out the output power at the receiving end. These two devices constitute an optical loss tester. When combining a light source and a power meter into a set of instruments, it is often referred to as an optical loss tester (also known as an optical multimeter). When we measure the loss of a link, one person needs to operate the test light source at the transmitting end and the other person uses the optical power meter to measure at the receiving end, so that only the loss value in one direction can be obtained.
Usually, we need to measure the loss in both directions (because there is a loss of the connection connection or it is due to the asymmetry of the transmission loss of the fiber). At this point, the technicians must exchange equipment and conduct measurements in the other direction. However, what should they do when they are separated by more than a dozen floors or tens of kilometers? Obviously, if both of them have a light source and an optical power meter, they can measure them on both sides at the same time. The advanced fiber test kits used for certification testing are now capable of two-way dual-wavelength testing. For example, Fluke's CertiFiber and DSP cable test series FTA fiber test kit.

In short, to complete an optical loss measurement, a calibrated light source and a standard optical power meter are indispensable.