The laser power and energy meter are mainly used to measure the output of the laser power. Regardless of whether the light emission comes from a weak light source (such as fluorescence) or a high-energy pulsed laser, power, and energy meters are indispensable tools in a variety of application environments such as laboratories, production departments, or work sites.

When the pyroelectric crystal is heated, the crystal will be polarized, so that polarized charges are generated at both ends of the crystal, and a metal layer is plated on both ends of the crystal to form a capacitor. Then, under the action of the temperature gradient, the polarized charge gathers at both ends of the capacitor to generate a voltage signal. The voltage signal is proportional to the temperature gradient formed by the heat converted by light absorbed by the detector film.

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Fluctuations in signal strength can be caused by variations in temperature of air pockets between the transmitter and receiver due to natural differences or objects such as buildings etc. This effect, know as refractive turbulence, causes image dancing or blurring of the signal at the receiver end which results in amplitude loss.

Free Space Optics wireless network ranges are typically found to be between around 100m and 2km but due to the nature of the signal strength being directly affected more by atmospheric conditions over increasing distance, the shorter the range between the two unit locations the higher the performance and availability of the connection will be.

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Free Space Optics Wireless Networks can only operate as Point-to-Point links between 2 units, however, when combined with LAN or WLAN networks they can provide very effective solutions to many scenarios such as:

Due to light not be able to travel through opaque mediums, objects such as birds, planes and people can momentarily cause interruptions to the service by blocking the Free Space Optics' light beam, with service resuming instantly when the light path is cleared. Multi-beam technology can be used with compatible systems to try and counter this problem.

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All Free Space Optics technology is strictly controlled to make sure that standards are followed to limit any dangers. On the whole, Free Space Optics units are of low enough power not to cause long term harm when the laser is exposed to a person's eye, however precautions should be taken so that this never occurs if possible.

Beam spread, or more technically called beam divergence, is measurable angular effect of the beam's dissipation at a constant rate as it travels further through the atmosphere.

The basis of Free Space Optics communication is rather straightforward with each unit housing an optical receiver and transmitter, allowing the sending and receiving of data simultaneously, and an optical source with a focusing lens. The unit at one location transmits a beam of focused light carrying the information directly at the unit at the receiving location where the light beam is then transferred to an optical fibre from a high sensitivity receiver.

Free Space Optics provides speeds comparable to those of optical fibre connections with the flexibility and practicality of being part of a wireless network providing bandwidth speeds typically advertised as up to 10Mbps, 100Mbps, 155Mbps and 1.25Gbps, with possible speeds of up to 10Gbps becoming likely in the future with the use of WDM (Wavelength-Division Multiplexing) technology. Currently, the only other wireless technology capable of these kinds of speeds is Millimetre Wave RF Wireless Networking which, in comparison, requires licensing and can affected severely by rain in the 60GHz range. Due to the received beam being transferred onto an optical fibre to connect to the core network, trouble free integration and easy set up make Free Space Optics networking's compatibility with any system very high.

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Free Space Optics (FSO) is a technology that uses laser beams via a line of sight optical bandwidth connection to transfer data, video or voice communications across areas ranging typically from 100m to a few kilometres at throughput bandwidths up to 1.25Gbps at frequencies above 300GHz of wavelengths, typically, 785 to 1550nm. Using Free Space Optics wireless networks eliminates the need to secure licensing found with RF signal solutions and also the expensive costs of laying fibre optic cable; principally the concept of transferring data via light is the same as with fibre optics just through a different medium.

Unlike rain and snow, that on the whole has little effect on Free Space Optics communication, fog and water vapour droplets are a real hindrance to the operating performance. The small water droplets can at points completely stop the light beams from being received due to light absorption, refraction scattering or even complete reflection which can significantly lower data rates. Therefore in foggy areas, Free Space Optics may not be the best solution, however applications have been successfully carried out that have provided acceptable reliability with redundancy systems in place. The following five points listed all refer to the signal attenuation caused by atmospheric conditions.

Beam wander or jitter is the amount that the centroid or peak value of the beam strength profile moves with time and can be caused by turbulence resulting in the beam becoming unfocused.

Due to being located above ground unlike, for the most part, laid fibre optic cable, different challenges are presented when considering Free Space Optics performance with the biggest being atmospheric conditions. However, most drawbacks and shortcomings can be resolved through the inclusion of redundancy systems and correct wireless network planning.

The laser probe is an absorber coated with thermoelectric material. The thermoelectric material absorbs most of the light energy and converts it into heat, and only a small part of it reflects. The ratio of absorption to reflection is related to the spectral response curve of the material. The heat storage body of the absorber and its thickness determine the speed of heat transfer to the probe and the reaction time. The temperature change of the probe can generate current, and the current is transformed into a voltage signal and transmitted through the sheet ring resistance.

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Power measurement is a process of obtaining the true value of power based on system and random errors, and there is a certain power uncertainty. For power measurement, there are two types of power, one is accuracy, the deviation between the measured value and the true value; the other is power stability, the range of power fluctuations measured repeatedly under the same condition. Specifically, the power meter can measure continuous wave (CW) or repetitive pulse light sources, and the sensors used are usually thermopiles or photodiodes. Energy meters are usually used to measure pulsed lasers, that is, single-pulse or repetitively pulsed light sources. The sensors used include pyroelectrics, thermopiles, or photodiodes with circuits specially designed for measuring pulsed light sources.

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Water vapour molecules in the air absorb the energy from photons (light particles) within the light beam which causes an overall loss in power density. The use of spatial diversity and correct system power helps combat this effect as absorption is more common at certain wavelength ranges of light.

Although laser power meters and energy meters are provided separately, with the development of general-purpose instrument panels or display devices capable of a large number of different types of optical sensors, they are also collectively referred to as a single type of instrument-power and energy meters. The laser power meter is generally composed of a thermopile or a photodiode. The thermopile is used to measure high power, and the photodiode is used to measure low power. The energy meter is composed of pyroelectric materials, which respond to pulse signals. Among them, the film layer that converts laser power into heat plays a very important role and is the core technology of laser power or energy meter.

The purpose of power meter calibration is to calibrate its own measurement accuracy to ensure that the measured value is within the error range of the power meter usage report, so as to ensure the normal use accuracy of the power meter. The power meter is calibrated with a third-party power meter. According to the factory calibration report, different powers are used to verify the accuracy and stability of the actual calibration of the power meter without damaging the power meter.

Building sway due to wind can be a problem as it disrupts the alignment between the two transceiver units causing loss of signal. Divergent beam technology can be used to allow the units to communicate in these situations but performance is still slightly affected.

Scattering occurs when certain wavelengths experience collisions with objects and are redistributed in varying directions without energy loss (unlike absorption). Scattering is more likely to have a more frequent and larger effect over long distances where it can have a significant effect on beam strength.

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The core part of the photodiode is a PN junction. When an appropriate reverse voltage is applied to the PN junction, no current flows through the PN junction due to lack of carriers. When photons irradiate the PN junction, the electrons or holes get rid of the constraints and form photo-generated carriers in the PN junction. The photo-generated carriers drift under the action of the electric field to form a current. The magnitude of the current and the energy of the incident light are Proportion. The photodiode is based on the photoelectric effect, which has a fast response time but is also prone to current saturation, and can only measure very small power.

Free Space Optics is a very secure method of wireless communications when compared to RF Signal Networks because the light beams cannot be detected by spectrum analysers, data transmissions can be encrypted, the laser beams are very narrow and invisible making them hard to find or detect and to receive the signal, another matching receiver would have to be aligned within the light path which is quite unlikely to happen.

The reaction time of the thermopile power meter is relatively slow, which is determined by its principle. The response time of the thermopile power depends on the heat transfer time required for the heat generated by the laser to be absorbed by the film on the surface of the power meter to transfer to the edge of the power meter disc. The greater the measurement power, the larger the diameter of the detection disc is generally required. For larger power meter probes, the time required for heat transfer is on the order of seconds, so the response time required by the superpower meter is also longer. Of course, there are also some specially designed thermocouple structures. The direction of measuring heat transfer is consistent with the direction of the laser. The thermocouple in this direction is made very thin and on the order of micrometers, which greatly reduces the time required for heat transfer. The thermal response time drops below milliseconds.

The pyroelectric probe is not suitable for detecting continuous or long pulse width laser, because the stored charge of the capacitor is easy to saturate or the capacitor only responds to AC or pulse signals.