Fiber Optic Power Meters with Internal Sensor

Overview
Specs
Pulse Calculations
Feedback

Fiber Optic Power Meter Features

InGaAs (PM20C or PM20CH) or Si (PM20A) Sensors
Wavelength Range:

400 nm - 1100 nm (Si)
800 nm - 1700 nm (InGaAs)

Power Ranges:

-60 dBm to 16 dBm (1 nW - 40 mW) for PM20A
-60 dBm to 13 dBm (1 nW - 20 mW) for PM20C
-50 dBm to 23 dBm (10 nW - 200 mW) for PM20CH

Interchangeable Fiber Connector, FC/PC Adapter Included (FC/APC, SC, ST, LC, or SMA Adapters Can be Ordered Separately)
Absolute and Relative Measurements Displayed in W, dBm, dB
NIST-Traceable Wavelength Calibration in 5 nm Steps
50 Hours of Operation Between Charges

The PM20 Series of Fiber Optic Power Meters are robust, full-featured, handheld instruments, which together cover the full range of optical fiber applications within the 400 - 1700 nm range with optical powers ranging from -60 dBm to +23 dBm (1 nW - 200 mW). A rugged enclosure, internal sensors, and kickstand make these models ideal for field or lab applications.

Functionality
Efficient, low-power circuitry provides long battery operation. The alphanumeric 8-digit LCD display allows easy power read-outs. The operation of the device is intuitive due to the clearly labeled key pad. All common features like wavelength setting, relative measurements, power read-out, and auto-shutdown are included. The PM20 is powered by a built-in rechargeable NiMH battery or by the included AC adapter that also recharges the battery. The unit comes with an FC fiber adapter that works with both FC/PC and FC/APC. Most industry standard fiber adapters (i.e. FC/APC, SMA, SC, ST, FC, and LC) are available for purchase and can be easily installed. Please note that we do not recommend removing the FC adapter for free-space applications due to difficulty aligning the beam onto the sensor’s 2 mm active area.

Each console comes with the following: the console with built-in sensor, FC fiber adapter (for FC/PC or FC/APC), 12 VDC power supply (PMPS12), Certificate of Calibration, and operating manual.

Power Meter Item #	PM20A	PM20C	PM20CH
Sensor Specifications
Optical Power Range	-60 dBm to 16 dBm (1 nW - 40 mW)	-65 dBm to 13 dBm (1 nW - 20 mW)	-50 dBm to 23 dBm (10 nW - 200 mW)
Spectral Range	400 - 1100 nm	800 - 1700 nm
Detector Type	Silicon	InGaAs
Sensor Size	3.6 x 3.6 mm	Ø2 mm
Input Aperture	3.6 x 3.6 mm	Ø2 mm
Aperture Thread	SM05 Thread (0.535"-40) for Fiber Adapters Fiber Adapter Included for FC Connectors (FC/PC or FC/APC)
Measurement Uncertainty	±0.25 dB
Measurement Standard	NIST Traceable
Optical Damage Threshold	50 W/cm²
General Console Specifications
Detector Compatibility	-
Display Type	Alphanumeric 8-Digits LCD
Display Format	4 Digit Read Out with Units and Symbols
Power Units	dBm, dB, nW, µW, mW
Resolution	14 bit
Sample Rate	10 Hz
Dimensions (H x W x D) w/ Holster	125 x 80 x 39 mm (4.9" x 3.1" x 1.5")
Weight	0.2 kg (0.44 lbs)
Operating Temperature	5 °C to 40 °C (Non-Condensing)
Storage Temperature	-20 °C to 70 °C
Power Management
Battery Operation	Internal NiMH Battery Pack, 150 mAh, 6 V
Operating Time	50+ Hours
Shutdown	Manual, Auto 5 Minutes, or Auto 60 Minutes
Charger	3-Hour Battery Charger Included
Charger Power Supply	Input: 90 - 264 VAC, 50 - 60 Hz; Output: 12 VDC @ 0.85 A

All technical data are valid at 23 ± 5 °C and 45 ± 15% relative humidity (non-condensing).

Pulsed Laser Emission: Power and Energy Calculations

Click above to download the full report.

Determining whether emission from a pulsed laser is compatible with a device or application can require referencing parameters that are not supplied by the laser's manufacturer. When this is the case, the necessary parameters can typically be calculated from the available information. Calculating peak pulse power, average power, pulse energy, and related parameters can be necessary to achieve desired outcomes including:

Protecting biological samples from harm.
Measuring the pulsed laser emission without damaging photodetectors and other sensors.
Exciting fluorescence and non-linear effects in materials.

Pulsed laser radiation parameters are illustrated in Figure 1 and described in the table. For quick reference, a list of equations are provided below. The document available for download provides this information, as well as an introduction to pulsed laser emission, an overview of relationships among the different parameters, and guidance for applying the calculations.

Equations:
Period and repetition rate are reciprocal:		and
Pulse energy calculated from average power:
Average power calculated from pulse energy:
Peak pulse power estimated from pulse energy:
Peak power and average power calculated from each other:
	and
Peak power calculated from average power and duty cycle*:
	*Duty cycle () is the fraction of time during which there is laser pulse emission.

Click to Enlarge

Figure 1: Parameters used to describe pulsed laser emission are indicated in the plot (above) and described in the table (below). Pulse energy (E) is the shaded area under the pulse curve. Pulse energy is, equivalently, the area of the diagonally hashed region.

Parameter	Symbol	Units
Pulse Energy	E	Joules [J]	A measure of one pulse's total emission, which is the only light emitted by the laser over the entire period. The pulse energy equals the shaded area, which is equivalent to the area covered by diagonal hash marks.
Period	Δt	Seconds [s]	The amount of time between the start of one pulse and the start of the next.
Average Power	P_avg	Watts [W]	The height on the optical power axis, if the energy emitted by the pulse were uniformly spread over the entire period.
Instantaneous Power	P	Watts [W]	The optical power at a single, specific point in time.
Peak Power	P_peak	Watts [W]	The maximum instantaneous optical power output by the laser.
Pulse Width		Seconds [s]	A measure of the time between the beginning and end of the pulse, typically based on the full width half maximum (FWHM) of the pulse shape. Also called pulse duration.
Repetition Rate	f_rep	Hertz [Hz]	The frequency with which pulses are emitted. Equal to the reciprocal of the period.

Example Calculation:

Is it safe to use a detector with a specified maximum peak optical input power of 75 mW to measure the following pulsed laser emission?

Average Power: 1 mW
Repetition Rate: 85 MHz
Pulse Width: 10 fs

The energy per pulse:

seems low, but the peak pulse power is:

It is not safe to use the detector to measure this pulsed laser emission, since the peak power of the pulses is >5 orders of magnitude higher than the detector's maximum peak optical input power.

Posted Comments:

dayana A (posted 2019-10-22 14:37:04.1)

Does Fiber Optic Power Meters have Built in Backlight feature ?

dpossin (posted 2019-10-24 08:47:59.0)

Hello Dayana, Thank you for your feedback! In case you mean a backlight for the display, unfortunately we currently do not offer this feature.

Priya R (posted 2019-10-21 22:45:44.04)

Hi, Is PM20CH integrated into a single unit for display and Keypad?

MKiess (posted 2019-10-25 09:31:06.0)

This is a response from Michael at Thorlabs. The Thorlabs PM20CH is a complete, easy to use fiber-optic power measurement system with built-in optical sensor. It has five operating keys and a display with which you can make all possible settings on the device itself.

user (posted 2019-04-15 10:14:54.383)

Hi! We have recently bought a PM20CH power meter almost a month ago. Initially just to check the device it was working properly. But while doing the experiments and with its constant use it is found that if the battery is full it works fine when no charger is attached to it but the moment you plug the charger it shows a constant smudged display which seems to be CHARGING and the screen is fixed with it and one can't do any measurements. What might be the reason for it? The device is certainly under warranty period.

swick (posted 2019-05-15 03:32:15.0)

This is a response from Sebastian at Thorlabs. The "charging" should disappear on the display after few seconds. As you did not left contact details on this feedback, please contact your local Thorlabs Office for immediate help.

user (posted 2018-11-20 01:52:38.42)

Hi! Actually I have been trying to measure and verify the power of a fiber laser which has a power stability of 0.1 % with PM20 CH fiber optic power meter but the reading of the power meter fluctuates and is not providing a stable output power reading. Can you please specify the stability of the power measured by this PM20CH power meter?

nreusch (posted 2018-11-28 05:51:35.0)

This is a response from Nicola at Thorlabs. Thank you for your inquiry! I am sorry to hear that you are not able to get a stable output reading. Unfortunately, we only specify an absolute uncertainty of +/-0.25 dB. The stability and repeatability of the PM20CH are definitely lower than this value. As you did not leave any contact information, please contact your local Tech Support team to discuss wavelength, absolute power and extent of fluctuations you are observing to check whether your PM20CH shows a normal behavior.

jan0dirk.lueuer (posted 2018-08-26 13:17:06.387)

Can this powermeter be used to measure short pulses (around 200 ns)? We tried measuring powers (approx. 150 mW) and see a lot less power than we get using power heads.

nreusch (posted 2018-08-29 06:59:26.0)

This is a response from Nicola at Thorlabs. Thank you very much for your inquiry. The PM20A contains a Silicon photodiode sensor. We do not recommend measuring nanosecond sources with this type of sensor. I will contact you directly to discuss alternative options.

srikanth (posted 2018-07-11 04:04:48.793)

What are implications for power measurements FC/APC connected pigtails? What are resolution (optical power) and linearity of the power meter? Is the power meter calibrated over entire wavelength range in steps of 5nm? LDT of 50W/cm^2 for (PM20CH) turns out to be ~32dBm; please confirm.

swick (posted 2018-07-13 05:26:30.0)

This is a response from Sebastian at Thorlabs. Thank you for the feedback. The linearity is +/- 0.5 % and the resolution depends on the power range but is basically 14 bit. For using FC/APC connectors we recommend to use PM20-FC as fiber adapter. The calibration step size is 5 nm over entire wavelength range. The damage threshold is specified to be 50 W/cm² which is not necessarily equal to +32dBm because not the complete sensor size gets illuminated in most cases. This finally depends on the fiber type used.

ana.cardenas (posted 2018-06-19 13:50:16.06)

We aquired a PM20CH and we would like to know if it is possible to get an adapter for free space measurements.

mvonsivers (posted 2018-06-21 08:05:20.0)

This is a response from Moritz at Thorlabs. Thank you for your inquiry. The PM20 series is only designed for fiber coupled measurements, however, for free space beams the fiber adapter could just be removed.

Dee1g12 (posted 2017-11-22 18:06:31.78)

Can the charger be bought separately? If so, how much do they cost? Thanks, Sincerely, -David-

mvonsivers (posted 2017-11-27 08:42:52.0)

This is a response from Moritz at Thorlabs. Thank you for your inquiry. Currently we do not offer a replacement power supply as standard product. However, any power supply with the following specifications can be used: 12V, 850mA, 2.1mm/5.5mm plug. I will contact you directly for further information.

schaefer (posted 2017-02-15 14:08:06.713)

Hi! We have used a P20A unit for a long time and it seems like the battery has suffered quite a bit - after recharging it until 'battery is full' it takes only a couple of minutes until it says 'battery low' and with the AC plugged in there is a constant 'charging' text getting in the way of the actual measurement. Is there any way to replyce the battery or at least turn of the recharging message blinking?

wskopalik (posted 2017-02-21 03:16:46.0)

This is a response from Wolfgang at Thorlabs. Thank you very much for your inquiry. Yes, we can exchange the battery in these powermeters. I have contacted you directly to arrange the exchange.

nicholas.sinclair (posted 2014-08-21 08:36:54.13)

Just a follow-up to the previous response about the active area of the PM20A. The specs on the webpage say 3.6 mm^2, but the manual says (3.6 mm x 3.6 mm), which is correct? Since you mentioned the possibility of the beam being too large at the sensor, I'm curious what is the max acceptable NA for a single-mode fiber to avoid this issue (or if you could just tell me the approximate distance from the fiber tip to the sensor). Thanks!

shallwig (posted 2014-08-22 10:04:06.0)

This is a response from Stefan at Thorlabs. Thank you very much for your inquiry.The sensor size is like stated in the manual on page 10 3.6mm x 3.6mm http://www.thorlabs.com/thorcat/14100/PM20A-Manual.pdf I am sorry if the information on the website were confusing here. The distance between ferule and detector plane is 3,7 +/- 0,3mm. I will contact you directly to discuss you application in detail.

user (posted 2014-04-17 17:17:37.477)

Dear Tech-support, could you please confirm if PM20A is compatible with standard 1mm POF (@650nm and 850nm)? best regards Michal

shallwig (posted 2014-04-25 04:12:55.0)

This is a response from Stefan at Thorlabs. Thank you very much for your inquiry. To decide if a fiber is suitable we would need to know the NA and diameter, since it is possible to over illuminate the sensor. We specify the sensor size with 3.6 mm^2 active area. If the beam is larger, in the plane of the sensor, you will loose light and measure accuracy will be effected. Also, the damage threshold of the sensor may be an issue. We specify a damage threshold of 50 W/cm2. If your fiber has one of the standard connectors, you can exchange the FC/PC adapter for one of the adapters we provide as accessories on our website: http://www.thorlabs.de/newgrouppage9.cfm?objectgroup_id=906. Regarding the wavelength range, both 650nm and 850nm lie within the specified wavelength range of the built-in Si detector. To discuss in more detail the compatibility of your specific light source + fiber unit with our PM20A I will like to contact your directly.

bdada (posted 2011-12-13 11:59:00.0)

Response from Buki at Thorlabs: We have contacted you to get more information about your request.

p_a_t_g (posted 2011-12-13 09:32:37.0)

Gentlemen The power to put has function of guarded information

jjurado (posted 2011-03-22 10:43:00.0)

Response from Javier at Thorlabs to anjonslay: Thank you very much for your interest in our products. A representative from our China sales office will contact you directly with pricing and availability information for our PM20C power meter. You can also reach this office via phone or e-mail: Phone: +86 (0)21-32513486 or +86 (0)21-32513482 Email: chinasales@thorlabs.com

anjonslay (posted 2011-03-22 17:24:06.0)

??! ?????????????????????????:PM20C - Fiber Power Meter,?????:PM20-FC - FC Fiber Adapter Cap with internal SM05 Thread?????,????????????,???????????????!?????????????????????????????????????????!?????!??! ??????! ??/????/??????

deriksson (posted 2009-12-28 09:27:01.0)

PM20A passar utmärkt för att mäta effekten ur en laser diod med den effekt och vågläng som du vill mäta. PM20A är lättanvänd och effekten läses ut direkt på displayen Till PM20A finns dessutom olika fiber adaptrar under sectionen Accessories. The PM20A will work perfect for measuring the power of the laser diode you want to measure. The PM20A is easy to use and the power can be read directly on the display. Different fiber connectors are available under the section Accessories

mats (posted 2009-12-27 13:19:08.0)

Hej - jag jobbar med laserbehandlingar mot tunnhårighet. Vi vill nu jämföra lasrar på marknaden. Alla lasrar på denna marknad säger sig ge 5mW av 650nm våglängd. Dioderna är fastsatta på plattor så jag måste ha en bärbar enhet för att komma åt att mäta eller om det finns någon fiberadapter att sätta mot dioden och att mätinstrumentet står på ett bord bredvid. Tror ni att ni har någon sådan produkt för oss? Det är inte superprecision jag är ute efter men absolut ingen leksak heller. Mats Stolt 0701 910 110 - 08 20 00 18

technicalmarketing (posted 2008-01-04 11:56:03.0)

The PM20C does indeed come with a FC-adaptor. That item is available under the "accessories" section in case you need to purchase another one. The ST adaptor is avilable using the orer code (PM20-ST). Shortly, you will also see an LC adapter featured on this page (PM20-LC). We hope this information is helpful and apologize for the confusion.

ruudg (posted 2008-01-04 05:52:49.0)

dear madam/sir recently I have ordered a PM20C from you, plus some extra adaptors. there is some small discrepancy here: in the specs from the PM20C it says that it comes with an FC adaptor included, and that SC, ST and SMA can be ordered as extras. however in the list of extras you can only choose FC (again?) SC and SMA. can you please check with what standard adaptor the PM20C really comes and/or provide me with an ordering code for the ST-adaptor? By the way, when will you be delivering the ordred PM20C? regards, ruud groenewegen. royal nioz, netherlands.

technicalmarketing (posted 2007-10-08 10:39:42.0)

Thank you for suggestion for this page. We now list power ranges in decibels as well as milliwatts. We hope this added information is helpful.

acable (posted 2007-10-05 20:30:24.0)

Since we don't all think in dB can you also provide power range in units of mW.

View All »Matching Part Numbers

Fiber Optic Power Meters with Internal Sensor

Fiber Optic Power Meter Features

Pulsed Laser Emission: Power and Energy Calculations

Fiber Optic Power Meters with Internal Sensor

Fiber Adapters for PM20 Power Meters

12 VDC Replacement Power Supply