Whether installing a new fiber or overhauling an old one, optical power meters have always played an important role in fiber inspection as a tool to measure power and detect loss.
- Optical power meter key analysis
The operation of the optical power meter is very simple, and most optical power meters have at least 4 buttons:
Measured value unit display key (displayed in dBM or W)
Reference key for measurement results
Wavelength selection key.
The function keys of different brands of optical power meters are not all the same, but they are basically the same.
- What is optical power?
In layman's terms, optical power is the "brightness" or "intensity" of light. Milliwatts (mw) and decibel milliwatts (dbm) are commonly used in fiber optic networks to express the unit of optical power.
- How to measure power with an optical power meter
Turn on network optics and measure transmitter or receiver power with only an optical power meter and a fiber optic connector adapter.
Before measuring power, the wavelength and other parameters of the optical power meter must be set within the specified range;
After everything is ready, you can connect the optical power meter to the transceiver end to measure the power of the receiver, or you can connect it to the light source end to measure the power of the transmitter;
Finally, write down the measured value and compare it with the power value specified by the device to see if it is within the specified floating range.
Here, we should pay attention to the interface of the optical power meter and the interface of the network optical device, and equip the appropriate fiber test jumper according to these situations.
For example, if the optical power meter interface is SC and the network optical device is LC, then an SC to LC fiber jumper should be equipped. Single-mode jumpers are used to measure single-mode optical power, and multi-mode jumpers are used to test multi-mode optical power.
- What is fiber loss
In addition to measuring optical power, an optical power meter can also measure fiber loss with a light source. What is fiber loss? How to measure fiber loss with an optical power meter?
Fiber loss refers to the light energy lost during the propagation of light in the fiber. These losses are mainly caused by the absorption of the fiber material, the conversion of light energy to thermal energy (heating), and the scattering of light. We also call this fiber loss "optical attenuation."
Fiber attenuation is the attenuation per unit length of fiber in dB / km.
When connecting two fibers, any connector or splice will have a loss inside. We call this loss"insertion loss", that is, the attenuation caused by the insertion of the device.
The size of the insertion loss is closely related to the quality of the optical fiber connector and the connection state of the optical fiber.
In addition, insertion loss can also refer to the loss within the multiplexer, as the fiber also generates losses when inserted into the multiplexer.
- How to measure fiber loss with an optical power meter and light source
Fiber loss is the optical energy lost during the propagation of light in the fiber. To measure fiber loss, not only an optical power meter is required, but also a light source.
Generally speaking, an 850/1300nm LED light source is required to measure the fiber loss of multimode fiber, and 1310/1550nm laser light source is required to measure the fiber loss of single-mode fiber.
In addition, in order to accurately measure fiber loss, it is necessary to make the test environment and conditions of the fiber and connector similar to the actual operating conditions.
That is to say, select a suitable light source and optical cable, and the optical cable has a standard transmission power, and has no influence on the power of the light source.
There are currently two main methods for measuring optical fiber loss: the single-ended loss measurement method and the double-ended loss measurement method.
The single-ended loss measurement method uses only the transmitting optical cable, while the double-ended loss measurement method uses a receiving optical cable connected to the power meter in addition to the transmitting optical cable.
The single-ended loss measurement method can measure the loss caused by the connection of the connector to the launch cable and the loss caused by the fiber, splice or other connector.
Therefore, each connector can be tested individually, which is the best way to measure fiber patch cords;
The double-ended loss measurement method can measure the loss in both connectors and all fibers, including the loss between the connector and the splice.
- Four key factors for buying an optical power meter
There are various types of optical power meters. Which one is right for us? When buying an optical power meter, we should also consider the following factors:
Ordinary optical power meters can generally test the absolute optical power of ordinary optical fiber links. However, in some special applications, such as passive optical networks (PON), course wavelength division multiplexing (CWDM) systems, etc., it is necessary to use PON optical power. Power meter and CWDM optical power meter to quickly and accurately measure the optical power of the corresponding line.
(2) Wavelength range
Different optical power meters have a certain working wavelength range, generally between 800nm and 1700nm.
If we want to measure the optical power of the line more accurately, we need to calibrate the wavelength of the optical power meter before measurement to make it consistent with the working wavelength of the fiber optic equipment.
Most fiber optic equipment now operates at 850nm, 1310nm or 1550nm, so it is best to ensure that the wavelength range covers these three wavelengths when purchasing optical power.
(3) Power measurement range
The power range that an optical power meter can measure has a significant impact on the accuracy of the measurement results.
In general, the power measurement range for optical power for common applications should be between -70dBm and +30dBm.
(4) Interface type
When measuring optical power, it is usually necessary to use an optical fiber jumper to connect the optical power meter and the test link. In this case, the interface type of the optical power meter must be consistent with the connector interface of the optical fiber jumper.
In the past, the interface of the optical power meter was fixed. For example, many optical power meters had only one FC interface, which was very inconvenient to use;
Now, some optical power plants adopt the design of a general interface, and some are also equipped with MPO / MTP multicore interface, which is much more flexible in measurement.
If the interface type of the optical power meter is inconsistent with the connector interface of the fiber optic patch cord, you can also purchase two different fiber optic patch cords. For example, if the optical power meter interface is SC and the optical network device is LC, then you can configure an SC to LC switch fiber jumper.