Introduction to Optical Power and Optical Power Meters

What is optical power?

Optical power in English for luminous power, is the work done by the light in a unit of time. Optical power unit commonly used milliwatts (mw) and decibels milliwatts (dbm) to indicate, where the relationship between the two: 1mW = 0dBm, less than 1mw decibel milliwatts for the negative value. Optical power is the basic and common parameters of optical signal measurement.

Second, what is the optical power meter? The role and type of optical power meter

Optical power meter in English for optical power meter, is used to measure the absolute optical power or optical power through a section of optical fiber relative loss instrument. In fiber optic systems, measuring optical power is the most basic measurement, like a multimeter in electronics; in fiber optic measurements, optical power meters are commonly used meters. By measuring the absolute power of the transmitter or optical network, an optical power meter is able to evaluate the performance of the optical equipment. Used in combination with a stabilized light source, an optical power meter can measure connection loss, verify continuity, and help assess the quality of fiber optic link transmission.

 

Optical power measurement is essential for the manufacture, installation, operation and maintenance of any fiber optic transmission system. In the fiber optic world, no engineering, laboratory, manufacturing plant or telephone maintenance facility can work without an optical power meter. For example, an optical power meter can be used to measure the output power of laser and LED light sources; to confirm the loss estimation of fiber optic links; and, most importantly of all, it is a key instrument for testing the performance specifications of optical components (optical fibers, connectors, splices, attenuators, etc.).

 

Optical power meter according to the built-in photodetector area is divided into: 1, the diameter of about 5mm large-area photodetector, suitable for the measurement of parallel beams; 2, the diameter of less than 1mm of small-area photodetector, its higher sensitivity and low cost, the disadvantage is difficult to calibrate.

 

Third, how to choose the optical power meter?

To select the appropriate optical power meter, consider the following four elements: 1, select the optimal probe type and connector interface type (LC, MPO or MTP, SC, ST, FC, MT-RJ). 2, evaluation of the calibration accuracy and manufacturing calibration procedures to match the range of optical fibers and connector requirements. 3, to determine that these models are consistent with the measurement range and display resolution. 4, with direct insertion loss dB function of the measurement.

 

First of all, the optical probe is the component that should be most carefully selected among all the properties of an optical power meter. The optical probe is a solid-state photodiode that receives coupled light from the fiber optic network and converts it into an electrical signal. It can be input to the probe using a dedicated connector interface, or adapted with a Universal Connector Interface UCI (using a screw-in connection), which accepts most industry-standard connectors. Based on the calibration factor for the selected wavelength, the optical power meter circuitry converts the probe output signal to display the optical power reading in dBm on the screen. The most important criterion for selecting an optical power meter is to match the optical probe type to the intended operating wavelength range. It is worth noting that InGaAs performs well in all three transmission windows when making measurements. Compared to germanium InGaAs has flatter spectral characteristics in all three windows, higher measurement accuracy in the 1550nm window, as well as superior temperature stability and low noise characteristics.

 

Secondly the performance criteria of the fiber and connectors are consistent with the requirements of the system. It should be analyzed what causes the uncertainty of measurements with different connection adapters? It is important to fully consider other potential error factors. Although NIST (National Institute of Standards and Technology) has established American standards, the spectrum of similar light sources, optical probe types, and connectors from different manufacturers is uncertain.

 

Third determine the optical power meter model that meets the measurement range requirements. Expressed in dBm, the measurement range (range) is a comprehensive parameter that includes determining the minimum/maximum range of the input signal so that the optical power meter can be assured that all accuracy, linearity (generally determined to be +0.8dB), and resolution (usually 0.1dB or 0.01dB) meets the application requirements. The most important selection criterion for an optical power meter is the matching of the optical probe type to the intended operating range.

 

Finally, the optical power meter should have a dB function (relative power), which is very useful in measurements where the optical loss is read directly. Without the dB function, the technician would have to write down separate reference and measured values and then calculate the difference. Therefore, the dB function gives the user a relative loss measurement, thus increasing productivity and reducing manual calculation errors.

Fourth, the basic indicators of the optical power meter

Optical power meter basic indicators are mainly four: 1, wavelength range. This is related to the type of photodetector used inside the optical power meter, such as silicon detection.

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