Fixed Fiber Optic Attenuators, Single Mode

Single Mode, Fixed Attenuators from 3 dB to 25 dB
Operating Wavelength Ranges from 1240 - 1620 nm
FC/PC or FC/APC Connectors

FAK05

Fiber Attenuator / Terminator Kit, FC/APC Connectors (Not to Scale)

FA03T

1240 - 1620 nm
3 dB Attenuation

FA25T-APC

1240 - 1620 nm
25 dB Attenuation

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Overview
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Fiber Optic Attenuator Selection Guide
SM	Tabletop EVOAs with Power Lock
	Digital VOAs
	Electronic VOAs for System Integration
	Manually Variable Attenuators
	Fixed-Value Attenuators
PM	Digital VOAs
	Electronic VOAs for System Integration
	Manually Variable Attenuators
MM	Manually Variable Attenuators
MM	Fixed-Value Attenuators

Features

Attenuates Optical Signal
FC/PC or FC/APC Connectors
Kits Containing Six FC/PC or FC/APC Attenuators Available

Thorlabs' Single Mode Fixed Fiber Optic Attenuators allow one to attenuate an optical signal easily by plugging an FC/PC- or FC/APC-terminated fiber directly into the back end of the attenuator connector. The input of the attenuator has a 2.2 mm wide key female connector, making it compatible with both narrow key and wide key male connectors. The output of the attenuator has a 2.0 mm narrow key male connector (either FC/PC or FC/APC). These single mode attenuators are made with polarization-insensitive doped fiber to achieve the specified attenuation over operating wavelength ranges between 1240 - 1620 nm.

Every attenuator includes connector caps. For replacements, plastic FC connector and mating sleeve caps are available.

Posted Comments:

L K (posted 2025-02-17 14:47:36.05)

Can you please provide out-of-band performance data for 850nm? Thank you very much, LK

EGies (posted 2025-02-18 11:29:33.0)

Thank you for contacting Thorlabs. At 850nm, all the fixed fiber optic attenuators show lower attenuation than spec'd. For example, the FA20T, spec'd for 20dB attenuation, showed only about 5dB attenuation at 850nm when tested with a broadband light source. I have reached out to you directly with additional data.

M J (posted 2024-04-26 09:17:13.307)

Hello, Is it possible to either get specs for these attenuators at 785nm or to have custom ones made?

cdolbashian (posted 2024-05-06 01:58:34.0)

Thank you for reaching out to us with this request. I have sent you the out-of-band performance data which we have. Regarding the custom, at the time of posting this, we do not have custom wavelength ranges available for these components.

Andrew Schaffer (posted 2023-02-20 15:04:56.397)

I am looking at your Fixed Fiber Optic Attenuators, Single Mode and would be very interested in the data for these down to 400nm. We don't need well defined attenuation, just quick and easy attenuation of our light without adding bulky optical components. Thank you.

jgreschler (posted 2023-02-24 10:53:53.0)

Thank you for reaching out to Thorlabs. Unfortunately at this time we don't have data for these performance below 700nm, and the attenuation is generally not stable below the specified operating range. We recommend using one of the single mode VOAs as an alternative for shorter wavelengths.

user (posted 2022-05-10 15:08:51.54)

Is the Maximum Input Power listed below of 1W given for pulse peak power or for average power? I'm concerned that my ns laser pulses might damage the attenuators.

jgreschler (posted 2022-05-12 03:33:57.0)

Thank you for reaching out to Thorlabs. The 1W maximum power spec refers to average power when used in pulsed applications.

S A (posted 2022-02-18 11:04:34.3)

Hi, are these fixed attenuators polarisation maintaining? Many thanks.

jgreschler (posted 2022-02-22 02:14:25.0)

Thank you for reaching out to Thorlabs. The attenuators on this page are all single mode, non-PM design. We do have a selection of PM attenuators here https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=6162

Ron Guzman (posted 2021-10-05 13:28:04.61)

Hi, I am not seeing operating temperature specs for some/all of your posted information. I would think if you are qualifying/validating attenuation, filtering, etc., then that would be over a temperature range. Can you assist and/or start to include Operating Temperature Range? That will assist us in classifying some of your products as industrial/ruggedized vs mere commercial. In addition, if you are qualifying them by some testing via telecom/optical/industry compliance, that may merit good collaboration with customers. Many Thanks.

azandani (posted 2021-10-15 04:12:37.0)

Hello Ron, thank you for contacting Thorlabs. Is this specifically limited to these fixed fiber optic attenuators? If so, we do list an operating temperature range of -40 C to 85 C in the chart above the part numbers. Or perhaps do you mean including an operating temperature for all of the products? Are there specific products which do not include it that you wish to have it? I have reached out to you directly about this.

Abdul Rasheed (posted 2021-03-11 12:25:12.457)

Would need datasheet for this

YLohia (posted 2021-03-12 03:39:13.0)

Hello, unfortunately, we don't provide datasheets for these attenuators. That being said, all specs can be accessed via the spec tables on this page.

cbrideau (posted 2015-02-19 18:12:15.143)

Any chance of getting these for 1040 or 1064nm, FC/PC? I have a fiber laser at 1040nm with diagnostic ports for coupling to a spectrometer, but the signal is a bit strong and I'd need to cut it back substantially.

jlow (posted 2015-02-25 04:36:47.0)

Response from Jeremy at Thorlabs: We do not have these for lower wavelengths at the moment. For your application, would the VOA1064-FC (http://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=6161&pn=VOA1064-FC) work?

cbrideau (posted 2014-02-12 11:15:43.03)

A version of this in SMA for multimode fibers would be useful for use with your fiber-coupled spectrometers. I often need to attenuate my signal before capturing it to avoid saturation of the CCD in the spectrometer. A drop-in attenuator like this would be very convenient for these measurements.

pbui (posted 2014-02-27 04:33:11.0)

Thank you for your feedback. We will consider your suggestion for incorporating SMA fiber attenuators into our catalog in the future.

kirk.mckenzie (posted 2014-02-04 14:45:08.917)

Can you make these product at 1064nm, APC?

pbui (posted 2014-02-26 02:02:34.0)

Unfortunately, we are unable to offer custom fiber optic attenuators for 1064 nm.

lee.cairns (posted 2013-11-04 14:56:09.277)

Hi, Do these attenuators also work at 1um? It would be useful to have lower denominations, for example, 1,2 and 3dB attenuators? Then it is possible to create a chain with an attenuation of arbitrary attenuation to the nearest dB. Regards, Lee

pbui (posted 2013-11-06 02:01:22.0)

Response from Phong at Thorlabs: Our fiber optic attenuators use a short length of attenuating fiber which is only single-mode in the specified operating wavelength range. They can be used with shorter wavelengths, but the attenuation value will be different from the specified values, and the beam will no longer be single mode. Although it is possible to stack the attenuators to achieve various attenuation levels, please keep in mind that you will also have some insertion loss between each attenuator as well, so your overall attenuation will be higher than simply adding the attenuation specs together.

flint (posted 2013-04-29 10:18:29.563)

What is attenuation at 2 microns? Is SMF-28 fiber being used? Thanks! John Flint Q-Peak, Inc.

tcohen (posted 2013-05-15 12:13:00.0)

Response from Tim at Thorlabs to John: The FA10T uses doped attenuating fiber. The attenuation at 2050nm was measured to be 9.55dB.

tcohen (posted 2012-02-24 14:25:00.0)

Response from Tim at Thorlabs: Thank you for your feedback. We are continuously expanding our catalog and broadening our selection of fixed optical attenuators is currently being discussed. I have posted your feedback for our design engineers to see.

user (posted 2012-02-24 10:34:01.0)

How about fixed attenuators for all the other wavelengths Thorlabs is famous for supporting.

jjurado (posted 2011-07-13 13:29:00.0)

Response from Javier at Thorlabs to sankar.ramasubramanian: We currently do not offer fixed connectorized attenuators for use with LC connectors. The only other options that we are able to offer are SC and ST. I will contact you directly to help you find a suitable alternative.

sankar.ramasubramanian (posted 2011-07-13 04:19:22.0)

We are looking for fixed connectorized 10 dB attenuators with LC connectors. Please send us information if you have the same.

jjurado (posted 2011-05-15 14:51:00.0)

Response from Javier at Thorlabs to last poster: The performance of these attenuators decays very rapidly if they are used outside of the specified bands. Please contact us at techsupport@thorlabs.com to discuss the details of your application, and we will gladly help you find a suitable attenuator.

user (posted 2011-05-13 15:43:23.0)

Will the attenuator work for wavelength lower than the specifications?

Tyler (posted 2009-01-08 16:57:51.0)

A response from Tyler at Thorlabs to mjcooper1: We can supply this part as a custom order with lead times as short as one day. I will have a member of our technical support department contact you so that they can generate a quote. Thank you for letting us know about your product needs. I will post that there is a need to add an FC/APC attenuator to our stocked items to our internal forum.

mjcooper1 (posted 2009-01-08 06:17:47.0)

I am suprised there are no fixed attenuators with FC/APC connectors, which is what I need

peter.rodrigo (posted 2008-12-12 04:37:39.0)

Hi.Are all of these optical attenuators bidirectional, so that reflected light will experience the same degree of attenuation?-peter

g884513 (posted 2007-12-13 03:48:30.0)

Dear sir Is the VOA50-APC applicative to the attenuation of 980nm laser sources? sincerely Yeh

Fixed Fiber Optic Attenuators: FC/PC

Table G1.1 Specifications
Item # (Click for Photo)	FA03T	FA05T	FA10T	FA15T	FA20T	FA25T
Fiber Connector	FC/PC
Key Size	Universal (Female 2.2 mm Wide-Key Input, Male 2.0 mm Narrow-Key Output)
Attenuation^a	3 ± 0.5 dB	5 ± 0.5 dB	10 ± 0.7 dB	15 ± 1.0 dB	20 ± 1.0 dB	25 ± 1.3 dB
Operating Wavelength Range	1240 - 1620 nm
Attenuation Graph^b (Click for Details)
Transmission	50.1 ± 6.1%	31.6 ± 3.9%	10.0 ± 1.8%	3.2 ± 0.8%	1.0 ± 0.3%	0.32 ± 0.1%
Return Loss	≥40 dB
Maximum Input Power	1 W
Operating Temperature	-40 to 85 °C

This attenuation does not include insertion loss. This value was measured by using a detector in freespace, therefore additional losses can be expected if used as the intermediary element between two fiber-coupled components.
The shaded region in these plots indicates the operating wavelength range that we specify for each attenuator. Performance outside of this range is not guaranteed.

Fixed Fiber Optic Attenuators: FC/APC

Table G2.1 Specifications
Item # (Click for Photo)	FA03T-APC	FA05T-APC	FA10T-APC	FA15T-APC	FA20T-APC	FA25T-APC
Fiber Connector	FC/APC
Key Size	Universal (Female 2.2 mm Wide-Key Input, Male 2.0 mm Narrow-Key Output)
Attenuation^a,b	3 ± 0.5 dB	5 ± 0.5 dB	10 ± 1.0 dB	15 ± 1.0 dB	20 ± 1.0 dB	25 ± 1.5 dB
Operating Wavelength Range	1240 - 1620 nm
Attenuation Graph^c (Click for Details)
Transmission	50.1 ± 6.1%	31.6 ± 3.9%	10.0 ± 2.6%	3.2 ± 0.8%	1.0 ± 0.3%	0.32 ± 0.13%
Return Loss	≥60 dB
Maximum Input Power	1 W
Operating Temperature	-40 to 85 °C

The attenuation tolerance value takes into account alignment variability due to the universal key design. When mating connectors with different key sizes, the angled fiber tips may not come into full contact.
This measurement does not include insertion loss. This value was measured by using a detector in freespace, therefore additional losses can be expected if used as the intermediary element between two fiber-coupled components.
The shaded region in these plots indicates the operating wavelength range that we specify for each attenuator. Performance outside of this range is not guaranteed.

Fixed Fiber Optic Attenuator and Terminator Kits

Zoom

Table G3.1 Kit Contents
FAK03 FC/PC Attenuator Kit		FAK05 FC/APC Attenuator Kit
Item	Qty.^a	Item	Qty.^a
Fixed Fiber Optic Attenuators^b		Fixed Fiber Optic Attenuators^b
3 dB, FC/PC (FA03T)	1	3 dB, FC/APC (FA03T-APC)	1
5 dB, FC/PC (FA05T)	1	5 dB, FC/APC (FA05T-APC)	1
10 dB, FC/PC (FA10T)	1	10 dB, FC/APC (FA10T-APC)	1
15 dB, FC/PC (FA15T)	1	15 dB, FC/APC (FA15T-APC)	1
20 dB, FC/PC (FA20T)	1	20 dB, FC/APC (FA20T-APC)	1
25 dB, FC/PC (FA25T)	1	25 dB, FC/APC (FA25T-APC)	1
Fiber Optic Terminator / Light Trap^c		Fiber Optic Terminator / Light Trap^c
FC/PC Connector (FTFC1)	5	FC/APC Connector (FTAPC1)	5
Dust Caps		Dust Caps
Female, White	12	Female, Green	12
Male, Clear	25	Male, Green	25

Although these kits ship with the specified number of each component, the box is capable of accepting three additional attenuators per compartment and five additional terminators.
Please see Tables G1.1 and G2.1 for specifications for our fiber attenuators.
Please click here for a complete list of specifications for our fiber terminators.

Six Fixed Fiber Optic Attenuators for 1240 - 1620 nm with Attenuation Values Ranging from 3 to 25 dB
Five Fiber Optic Terminators / Light Traps for Use in the 400 - 2100 nm Wavelength Range
Additional 12 Female and 25 Male Dust Caps Included for Convenience
Versions Available with FC/PC or FC/APC Connectors
Packaged in a Compact Plastic Box with Nine Individual Compartments

Thorlabs' Fiber Optic Attenuator and Terminator Kits each contain six fixed attenuators, five terminators, and a selection of dust caps. Components in the FAK03 kit have FC/PC connectors while those in the FAK05 kit have FC/APC connectors. Each kit is packaged in a plastic box measuring 7.0" x 3.5" x 1.25" (177.8 mm x 88.9 mm x 31.8 mm) and has nine labeled compartments. The label on the lid indicates the contents, associated Thorlabs item number (where applicable), attenuation value and tolerance for the attenuators, and wavelength range and return loss for the terminators. Table G3.1 lists the description and quantity of each item included in these kits.