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Ultrafast Fiber Optic Photoreceivers

  • Four Models Cover the 700 to 1650 nm Wavelength Range
  • Internal Multimode or Single Mode Fiber with FC/PC Connector
  • Maximum Bandwidth of 25 GHz or 40 GHz


Multimode, 25 GHz,
750 - 1650 nm


Single Mode, 40 GHz,
1250 - 1650 nm

Input Panel of the RXM25AF

Related Items

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Ultrafast Photoreceivers
Item #
Fiber Wavelength
OEM Module
Item #
RXM25DFa 25 GHz Multimode 700 - 870 nm RX25DF
RXM25BF 25 GHz 750 - 1650 nm -
RXM25AFa 25 GHz Single
1250 - 1650 nm RX25AF
RXM40AFa 40 GHz 1250 - 1650 nm RX40AF
  • These instruments incorporate our OEM modules, also available separately.


  • Hermetically Sealed GaAs or InGaAs Amplified Detector Module
  • Multimode and Single Mode Fiber Options
    • RXM25BF and RXM25DF: Internal OM4 Multimode Fiber
    • RXM25AF and RXM40AF: Internal SMF-28 Single Mode Fiber
  • Two AC-Coupled RF Output Signals via 2.92 mm (K) Connector
  • Built-In DC Photocurrent Monitor
    • Digital Output Sent to Display
    • Analog Output via SMA Connector
  • Replacement Power Supply Available
  • Packaged Instrument Versions of Our OEM Module Photoreceivers

The RXM Series of Ultrafast Receivers includes multimode and single mode fiber-coupled photoreceivers with wide wavelength ranges. The core element of each detector is a fiber-coupled, hermetically sealed microwave detector module. For convenience and simplicity of use, the module is mounted inside a rugged aluminum housing that includes current monitor circuitry and a digital display of the DC photocurrent.

Our multimode detectors contain Ø50 µm core OM4 multimode fiber, while our single mode receivers contain Ø9 µm core SMF-28 single mode fiber. Optical input can be coupled from an FC/PC-terminated fiber via the narrow key FC bulkhead connector. While single mode detectors are intended for use with single mode fiber patch cables, our multimode detectors are designed to accept input from multimode or single mode optical fiber connectors, making them versatile measurement instruments for research and commercial applications. We offer multimode and single mode hybrid patch cables to facilitate connecting optical cables with different connector types and GRIN multimode patch cables for reduced modal dispersion.

Inverting and non-inverting RF signal outputs are available via dual female 2.92 mm RF connectors, which may be connected to a measurement instrument using suitable microwave cables or adapters. If only one RF output is being used, the unused port should be capped with a 50 Ω terminator; two are included with each receiver. Both RF ports may also be used simultaneously. Measurements of the DC photocurrent can be viewed using the digital display, and an SMA jack on the input panel provides the analog current monitor output signal. Please see the Operation tab for additional information on functionality and operation.

RF Receiver
Click to Enlarge

The RX25AF Ultrafast Photoreceiver Module is used in the RXM25AF Ultrafast Photoreceiver Instrument.

The receivers have a peaking adjuster, with either 4 or 8 discrete settings, and a gain adjuster, with 16 discrete settings. The gain adjustment changes the amplitude of the output swing for a given input signal while the peaking adjustment changes the shape of the frequency response. A larger peaking value corresponds to higher magnitudes at high frequencies. By utilizing these two adjustments, a user can maximize the performance of the receiver for a specific application.

Included with each RXM series photoreceiver is a power adapter with a mini-B USB plug and a mounting bracket (ECM175, also available below) that snaps onto the side of the housing. The ECM175 bracket has a #8 (M4) counterbore, which allows easy mounting to a post or any other component with an 8-32 (M4) threaded hole.

Webpage Features
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We Design, Develop, and Manufacture Equipment up to 70 GHz

Questions? Demo Unit Requests?

Custom or OEM Applications?

Contact Us

Quick Start Guide

ESD Sensitive Components: Please note that the components inside the RXM series units are ESD sensitive. Take all appropriate precautions to discharge personnel and equipment before making any electrical connections to the unit. This especially applies to coaxial connecting cables that can accumulate capacitive charge.

Mounting the Detector: The included ECM175 mounting clamp, also available below, has a single counterbore that accepts a 8-32 (M4) cap screw (not included). Screw the clamp to the desired base or post before snapping it to the side of the detector housing and securing it using the integrated 5/64" (2 mm) locking screw.

RF and Photocurrent Monitor Output: Connection cables attached to the RF output ports, shown in Figure 1, and SMA photocurrent monitor port, shown in Figure 2, must be properly shielded. Attach the RF output of the RXM series unit to the measurement instrument using suitable cables or adapters, such at Thorlabs' microwave cables and adapters. If only one RF port is used, cap the unused port with a 50 Ω terminator; two are included with each unit. The measurement instrument must have a 50 Ω input and adequate bandwidth to resolve the high-speed signal from the RXM series ultrafast receiver.

Optical Fiber Input: Ensure the input optical power does not exceed +10 dBm. The FC/PC bulkhead connector used to couple the optical input signal to the detector is located on the input panel of the unit, shown in Figure 2. Fiber connector tips should be cleaned properly before making any connections. Input fiber for single mode detectors should be SMF-28 or equivalent. Input fiber for multimode detectors should be OM4, SMF-28, or equivalents.

DC Photocurrent Monitor: The DC photocurrent can be monitored directly by viewing the built-in digital display shown in Figure 3, as well as by using most voltmeters to read the analog voltage signal output via the high-impedance SMA jack located on the input panel shown in Figure 2. The units on the displayed digital current measurement can be toggled between µA and mA using the button on the front panel. There may be a small discrepancy (within specification) between the screen and SMA monitor output signal. The digital display reports a wide range of current values, up to 20 mA with a resolution of 1 nA, with the display automatically changing range in response to the signal magnitude. The analog voltage signal sent to the SMA connector has a linear relationship with the measured DC photocurrent up to 3.5 V: the transimpedance gain of the current monitor provides 200 mV per 1 mA of photocurrent. This linear relationship limits the current range reported by the analog SMA output signal, so that the range is smaller than that provided by the digital display.

Cleaning the Housing: Use a soft cloth moistened with mild glass cleaner. Do not spray directly onto unit.

Housing Features

While the RXM25AF receiver is shown below, these features are representative of all items on the page.

DXM20AF Output Panel
Click to Enlarge

Figure 1: Output Panel
DXM30AF Input Panel
Click to Enlarge

Figure 2: Input Panel
DXM25CF Top Panel
Click to Enlarge

Figure 3: Front Panel
Label Feature
R1 RF Output
(Female 2.92 mm, Inverting)
R2 RF Output
(Female 2.92 mm, Non-Inverting)
Label Feature
L1 2.0 mm Narrow Key FC/PC
(FC/APC Available Upon Request)
L2 SMA Jack; 5 in-lbs Torque Spec
L3 Peaking Adjuster
L4 Power Switch
L5 Mini-B USB Power Jack for +5 VDC Input
L6 Gain Adjuster
Label Feature
F1 Photocurrent Monitor Display
(4.5 Characters)
F2 Range Toggle Switch

Components Included with the RXM Series Ultrafast Detectors

RXM40AF System Components
Click to Enlarge
Components of the RXM Series Ultrafast Receivers
(RXM40AF Photoreceiver Shown)

  • Receiver Head with Hermetically Sealed Detector Module and Built-In Current Monitor
  • DS5 +5 VDC USB Power Supply with Location-Specific Plug
  • USB 2.0 Type-A to Mini-B Cable
  • One ECM175 Aluminum Mounting Clamp
  • Two 2.92 mm 50 Ω Terminators

Janis Valdmanis, Ph.D. Optics
Ultrafast Optoelectronics
General Manager

Custom and OEM Options

When your application requirements are not met by our range of catalog products or their variety of user-configurable features, please contact me to discuss how we may serve your custom or OEM needs.

Request a Demo Unit

Explore the benefits of using a Thorlabs high-speed instrument in your setup and under your test conditions with a demo unit. Contact me for details.

Contact Me
MX40B with cover removed
Click to Enlarge

The MX40B Digital Reference Transmitter

Design, Manufacturing, and Testing Capabilities

Thorlabs' Ultrafast Optoelectronics Team designs, develops, and manufactures high-speed components and instrumentation for a variety of photonics applications having frequency responses up to 70 GHz. Our extensive experience in high-speed photonics is supported by core expertise in RF/microwave design, optics, fiber optics, optomechanical design, and mixed-signal electronics. As a division of Thorlabs, a company with deep vertical integration and a portfolio of over 20,000 products, we are able to provide and support a wide selection of equipment and continually expand our offerings.

Our catalog and custom products include a range of integrated fiber-optic transmitters, modulator drivers and controllers, detectors, receivers, pulsed lasers, variable optical attenuators, and a variety of accessories. Beyond these products, we welcome opportunities to design and produce custom and OEM products that fall within our range of capabilities and expertise. Some of our key capabilities are:

  • Detector and Receiver Design, to 70 GHz
  • Fiber-Optic Transmitter Design, to 70 GHz
  • RF & Microwave Design and Simulation
  • Design of Fiber-Optic and Photonics Sub-Assemblies
  • High-Speed Testing, to 70 GHz
  • Micro-Assembly and Wire Bonding
  • Hermetic Sealing of Microwave Modules
  • Fiber Splicing of Assemblies
  • Custom Laser Engraving
  • Qualification Testing

Overview of Custom and Catalog Products

Our catalog product line includes a range of integrated fiber-optic transmitters, modulator drivers and controllers, detectors, pulsed lasers, and accessories. In addition to these, we offer related items, such as receivers and customized catalog products. The following sections give an overview of our spectrum of custom and catalog products, from fully integrated instruments to component-level modules.

Fiber-Optic Instruments

To meet a range of requirements, our fiber-optic instruments span a variety integration levels. Each complete transmitter includes a tunable laser, a modulator with driver amplifier and bias controller, full control of optical output power, and an intuitive touchscreen interface. The tunable lasers, modulator drivers, and modulator bias controllers are also available separately. These instruments have full remote control capability and can be addressed using serial commands sent from a PC.

  • Fiber-Optic Transmitters, to 70 GHz
  • Linear and Digital Transmitters
  • Electrical-to-Optical Converters, to 70 GHz
  • Modulator Drivers
  • Modulator Bias Controllers
  • C- and L-Band Tunable Lasers

Customization options include internal laser sources, operating wavelength ranges, optical fiber types, and amplifier types.

Fiber-Optic Components

Our component-level, custom and catalog fiber-optic products take advantage of our module design and hermetic sealing capability. Products include detectors with frequency responses up to 50 GHz, and we also specialize in developing fiber-optic receivers, operating up to and beyond 40 GHz, for instrumentation markets. Closely related products include our amplifier modules, which we offer upon request, variable optical attenuators, microwave cables, and cable accessories.

  • Hermetically-Sealed Detectors, to 50 GHz
  • Fiber-Optic Receivers, to 40 GHz
  • Amplifier Modules
  • Electronic Variable Optical Attenuators
  • Microwave Cables and Accessories

Customization options include single mode and multimode optical fiber options, where applicable, and detectors optimized for time or frequency domain operation.

Free-Space Instruments

Our free-space instruments include detectors with frequency responses around 1 GHz and pulsed lasers. Our pulsed lasers generate variable-width, nanosecond-duration pulses, and a range of models with different wavelengths and optical output powers are offered. User-adjustable repetition rates and trigger in/out signals provide additional flexibility, and electronic delay-line products enable experimental synchronization of multiple lasers. We can also adapt our pulsed laser catalog offerings to provide gain-switching capability for the generation of pulses in the 100 ps range.

  • Pulsed Lasers with Fixed 10 ns Pulse Duration
  • Pulsed Lasers with Variable Pulse Width and Repetition Rates
  • Electronic Delay Units to Synchronize NPL Series Pulsed Lasers
  • Amplified Detectors

Customization options for the pulsed lasers include emission wavelength, optical output powers, and sub-nanosecond pulse widths.

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25 GHz Photoreceivers

Item #a Full
Fiber Type Bandwidth Wavelength
Responsivity Conversion
Optical Return
Loss (Max)
Power (NEP)c
Current Monitor
RXM25DF info Ø50 µm MM OM4 500 kHz - 25 GHz 700 - 870 nm 0.5 A/W 75 - 4800 V/W -14 dB 24 pW/√Hz 200 mV/mA
RXM25BF info Ø50 µm MM OM4 500 kHz - 25 GHze 750 - 1650 nm 0.75 A/W 110 - 7200 V/W -12 dB 15 pW/√Hz
RXM25AF info Ø9 µm SMF-28 500 kHz - 25 GHz 1250 - 1650 nm 0.75 A/W 110 - 7200 V/W -28 dB 15 pW/√Hz
  • All specifications are typical at 25 °C, into 50 Ω, and at 850 nm (RXM25DF), 1310 nm (RXM25BF), or 1550 nm (RXM25AF) unless otherwise noted.
  • Differential and Discretely Adjustable; Data Shown in Graph are Typical
  • At Maximum Gain Setting
  • DC Level Proportional to Avg. Photocurrent
  • At 1550 nm
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
RXM25DF Support Documentation
RXM25DFMultimode Ultrafast Receiver, 700 - 870 nm, 500 kHz - 25 GHz, FC/PC
5-8 Days
RXM25BF Support Documentation
RXM25BFNEW!Multimode Ultrafast Receiver, 750 - 1650 nm, 500 kHz - 25 GHz, FC/PC
RXM25AF Support Documentation
RXM25AFSingle Mode Ultrafast Receiver, 1250 - 1650 nm, 500 kHz - 25 GHz, FC/PC

40 GHz Photoreceiver

Item #a Full
Fiber Type Bandwidth Wavelength
Responsivity Conversion
Optical Return
Loss (Max)
Power (NEP)c
Current Monitor
RXM40AF info Ø9 µm SMF-28 300 kHz - 40 GHz 1250 - 1650 nm 0.7 A/W 140 - 3650 V/W -28 dB 21 pW/√Hz 200 mV/mA
  • All specifications are typical at 25 °C, into 50 Ω, and at 1550 nm unless otherwise noted.
  • Differential and Discretely Adjustable; Data Shown in Graph are Typical
  • At Maximum Gain Setting
  • DC Level Proportional to Avg. Photocurrent
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
RXM40AF Support Documentation
RXM40AFSingle Mode Ultrafast Receiver, 1250 - 1650 nm, 300 kHz - 40 GHz, FC/PC
5-8 Days

Side Clamps

Mounted Photoreceiver
Click to Enlarge

RXM40AF Photoreceiver Mounted on Ø1" Post Using an ECM175 Aluminum Clamp
  • Post-Mountable Aluminum Clamps
  • Double-Sided Plastic Clamps (Sold in Packs of Two)
  • One ECM175 Clamp Is Included with Each RXM Series Photoreceiver

Each RXM Series Photoreceiver includes one ECM175 anodized aluminum clamp, which snaps onto the bottom of the detector's housing and is secured by tightening the flexure lock using the 2 mm (5/64") hex locking screw. Additional aluminum and plastic clamps are available separately. These clamps are part of Thorlabs' family of side clamps that are designed to securely mount Thorlabs' rectangular electronics housings.

Aluminum Clamps
The ECM175 clamp has a #8 (M4) counterbore on the bottom; the ECM225 has three of these counterbores. The counterbores allow these clamps to be mounted onto a Ø1/2" post or any surface with an 8-32 (M4) tap. The clamp must be mounted via the counterbored through hole before the electronics housing is attached, as the counterbore will not be accessible once the housing is secured in the clamp.

Double-Sided Plastic Clamps
The EPS175 and EPS225 ABS plastic clamps are sold in pairs and easily snap onto the side of the electronics housing. Each clamp is designed to attach two housings with a common side width.

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
ECM175 Support Documentation
ECM175Aluminum Clamp for Electronics Housing, 1.75"
ECM225 Support Documentation
ECM225Aluminum Clamp for Electronics Housing, 2.25"
EPS175 Support Documentation
EPS175Double-Sided Plastic Clamp for Electronics Housings, 1.75", Qty. 2
EPS225 Support Documentation
EPS225Double-Sided Plastic Clamp for Electronics Housings, 2.25", Qty. 2

Replacement 5 VDC Regulated Power Supply

Photo of Power Supply Adapters
Click for Details

Region-Specific Adapters for DS5
  • 5 VDC Regulated Power Supply
  • USB Type-A Port
  • Compatible with Our DXM and RXM Series of Ultrafast Detectors and Photoreceivers

The DS5 is a 5 V regulated power supply with a USB Type-A female port. It can be used with any USB-compatible device that accepts a 5 VDC output, and is directly compatible with our DXM series of ultrafast fiber optic detectors and our RXM series of ultrafast fiber optic receivers when used with the USB-AB-72 USB cable (sold separately). In addition to the USB-AB-72, we also offer other USB 2.0 cables. A region-specific adapter plug is shipped with the DS5 power supply unit based on your location.

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
DS5 Support Documentation
DS55 VDC, 2 A Regulated Power Supply with USB Type-A Port, 100/240 VAC
5-8 Days
USB-AB-72 Support Documentation
USB-AB-72USB 2.0 Type-A to Mini-B Cable, 72" (1.83 m) Long
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