Fiber Optic Power Meters with Internal Sensor

  • Wavelength Range: 400 - 1700 nm
  • Power Range: -60 dBm to 23 dBm
  • Interchangeable Fiber Connector


Fiber Optic Power Meter

Easy-to-Read Large Digital Display

PM20 Power Meter with Fiber Adapter Removed

Additional SM05-Threaded Fiber Adapters Available Separately




Related Items

Please Wait

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 Connectors:
    • PM20-FC Wide-Key FC/PC Adapter Included
    • FC/APC, SC, ST®, LC, SMA, or Ø2.5 mm Ferrule 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.

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. The PM20-25 ferrule adapter (sold separately) can be used to directly insert 2.5 mm ferrules without a connector. 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.

*ST® is a registered trademark of Lucent Technologies, Inc.

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

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. 



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:
Peak power calculated from average power and duty cycle*:
*Duty cycle () is the fraction of time during which there is laser pulse emission.
Pulsed Laser Emission Parameters
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 Description
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 Pavg 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 Ppeak 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 frep 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:
user  (posted 2024-03-29 16:32:54.717)
I have a PM20C instrument, and I found that when using the instrument without the adapter, a certain value is measured. However, when the adapter is connected, the value decreases. What causes this?
dpossin  (posted 2024-04-02 06:42:00.0)
Dear customer, Thank you for your feedback. I will reach out to you directly to discuss this with you.
Jose Manuel Suarez  (posted 2023-10-04 10:49:25.067)
Hi! I work in the optical lab at Royal Observatory of the Navy in San Fernando (Spain) and had an issue using this power meter. I had an OVERFLOW reading when measuring 515nm green light of around 20mW (measured also with PM100D power meter without problem). It is supposed that measuring range is up to 40mW, so it was strange. Thanks in advance, regards.
hkarpenko  (posted 2023-10-10 10:37:32.0)
Dear Jose, thank you for your feedback. I will contact you directly to discuss this issue with you.
qiaozhanduo qiao  (posted 2023-02-15 00:15:13.913)
hkarpenko  (posted 2023-02-16 07:48:56.0)
Dear customer, thank you for your feedback. In general you are right, the peak power and average power should be well under the power range of the sensor. Measuring pulsed laser sources with a photodiode can be challenging, since you would need a higher repetetion rate to measure the correct power. I will contact you directly to discuss this further with you.
user  (posted 2022-12-01 13:14:02.81)
We have a PM20A powermeter and want to use it to measure the light intensity (400-800 nm) coming out of a ferrule (the fiber has a 0.2 NA). What distance do you recommend between the ferrule and the sensor? And what is the optimal diameter the light beam must have on the sensor?
hchow  (posted 2022-12-01 10:32:43.0)
Dear Customer, thank you for your feedback. The distance between the ferrule while encapsulated in a FC/PC fiber adapter to the sensor's plane is 3.7 +/- 0.3 mm. If you remove the fiber adapter, then from the surface of the diode connector's surface to the sensor is 3.2 mm. While the beam diameter on the surface of the sensor is given by this equation: expanded beam at PD surface = 2*( 3.7*Tan(NA))+core size. Thank you.
Francis Guay  (posted 2021-07-13 02:49:14.527)
Does Thorlabs provide a calibration Service for this device?
MKiess  (posted 2021-07-15 06:08:10.0)
Dear Francis, thank you for your inquiry. Yes we offer calibration service for this fiber optic power meter. If you wish to do so, please send an e-mail with the article number and the serial number of the desired power meter to Afterwards we will send you all further information for sending in the meter for calibration. If you have any further technical questions regarding calibration, please feel free to contact our Tech Support.
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 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: 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:
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.
Back to Top

Fiber Optic Power Meters with Internal Sensor

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
PM20A Support Documentation
PM20AFiber Optic Power Meter, 400 nm - 1100 nm, -60 dBm to +16 dBm (1 nW - 40 mW)
Lead Time
PM20C Support Documentation
PM20CFiber Optic Power Meter, 800 nm - 1700 nm, -60 dBm to +13 dBm (1 nW - 20 mW)
PM20CH Support Documentation
PM20CHFiber Optic Power Meter, 800 nm - 1700 nm, -50 to +23 dBm (10 nW - 200 mW)
Back to Top

Fiber and Ferrule Adapters for PM20 Power Meters

These adapters are compatible with devices that feature external SM05 threading such as our S15xC Series Fiber Power Meter Sensors, PM160 wireless power meter, and the Fiber Optic Power Meters above. One PM20-FC wide-key FC/PC fiber adapter is included with each of the power meters sold above. For details on narrow versus wide key connectors, please see our Intro to Fiber tutorial.

The PM20-25 ferrule adapter is designed without a locking connector mechanism and accepts fiber patch cables with Ø2.5 mm ferrules for quick power meter measurements.

Item # PM20-FC2 PM20-FC PM20-APC2a PM20-APCa PM20-SMA PM20-ST PM20-SC PM20-LC PM20-25
Adapter Image
(Click the Image
to Enlarge)
PM20-FC2 PM20-FC PM20-APC2 PM20-APC PM20-SMA PM20-ST PM20-SC PM20-LC PM20-25
Connector Type FC/PC,
2.0 mm Narrow Key
2.2 mm Wide Key
2.0 mm Narrow Key
2.2 mm Wide Key
SMA ST®b/PC SC/PCc LC/PC Ø2.5 mm Ferrule
Threading Internal SM05 (0.535"-40)
  • The PM20-APC and PM20-APC2 are designed with a 4° mechanical angle to compensate for the refraction angle of the output beam.
  • ST® is a registered trademark of Lucent Technologies, Inc.
  • In certain angle-independent applications, this adapter may also be used with SC/APC connectors.
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
PM20-FC2 Support Documentation
PM20-FC2FC/PC Fiber Adapter Cap with Internal SM05 (0.535"-40) Threads, Narrow Key (2.0 mm)
PM20-FC Support Documentation
PM20-FCFC/PC Fiber Adapter Cap with Internal SM05 (0.535"-40) Threads, Wide Key (2.2 mm)
PM20-APC2 Support Documentation
PM20-APC2FC/APC Fiber Adapter Cap with Internal SM05 (0.535"-40) Threads, Narrow Key (2.0 mm)
PM20-APC Support Documentation
PM20-APCCustomer Inspired! FC/APC Fiber Adapter Cap with Internal SM05 (0.535"-40) Threads, Wide Key (2.2 mm)
PM20-SMA Support Documentation
PM20-SMASMA Fiber Adapter Cap with Internal SM05 (0.535"-40) Threads
PM20-ST Support Documentation
PM20-STST/PC Fiber Adapter Cap with Internal SM05 (0.535"-40) Threads
PM20-SC Support Documentation
PM20-SCSC/PC Fiber Adapter Cap with Internal SM05 (0.535"-40) Threads
PM20-LC Support Documentation
PM20-LCCustomer Inspired! LC/PC Fiber Adapter Cap with Internal SM05 (0.535"-40) Threads
PM20-25 Support Documentation
PM20-25Customer Inspired! Ø2.5 mm Ferrule Adapter Cap with Internal SM05 (0.535"-40) Threads
Back to Top

12 VDC Replacement Power Supply

Click for Details
Region-Specific Adapters for the PMPS12
  • Replacement Power Supply for the PM20 Series Power Meters Sold Above
  • 12 VDC Power Supply
  • 90 - 264 VAC Input Voltage
  • Region-Specific Adapters Included
  • UL and CE Compliant

The PMPS12 is a 12 VDC power supply with a 1.8 m cable and 5.5 mm outer diameter DC connector. It operates at an input voltage of 90 - 264 VAC, and has a maximum current of 850 mA. This power supply ships with region-specific adapters included, shown in the image to the right.

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
PMPS12 Support Documentation
PMPS1212 VDC Power Supply for PM20 Series Power Meters
7-10 Days