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High-Speed Photoreceiver Module, Fiber-Coupled OEM Package

  • InGaAs Receiver for 1250 to 1650 nm Wavelength Range
  • RF Output Signal via Dual GPPO® Output Connectors
  • Adjustable Gain and Frequency Response Shape (Peaking)
  • Integrated SM Fiber Pigtail with FC/PC Connector
  • 40 GHz Bandwidth


Single Mode, 40 GHz,
1250 - 1650 nm

Compact, Hermetically Sealed Package for OEM Applications

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

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  • 1250 - 1650 nm Wavelength Range
  • InGaAs Detector with Transimpedance and Variable Gain Amplifiers
  • High-Speed Photoreceiver with Smooth Frequency Response for Bandwidths up to 40 GHz
  • AC-Coupled, Current Mode Logic (CML) Differential RF Output via Dual GPPO® Connectors
  • Manual or Automatic Gain Control
  • Pigtailed SMF-28 Single Mode Fiber
  • Hermetically Sealed Compact Package and Easy Integration Ideal for OEM Applications
  • Discounts for High-Volume Purchases Available; Contact Tech Support with Inquiries

The RX40AF photoreceiver is an amplified InGaAs detector with a transimpedance amplifier, variable gain amplifier, and 50 Ω buffer, as illustrated in the diagram below. It features adjustable gain, adjustable frequency response shape (peaking), and flat group delay (and/or frequency response), making it excellent for time domain measurements. The receiver also offers an automatic gain control option for maintaining constant output when input levels vary. Each detector consists of a fiber-coupled, hermetically sealed microwave detector module that enables it to be easily used for OEM applications (see the Operation tab for details).

The RX40AF photoreceiver utilizes a 9 µm core SMF-28 single mode fiber, and optical input can be coupled from an FC/PC-terminated fiber via the FC bulkhead connector. Users can purchase single mode hybrid patch cables to facilitate the connection of optical cables with different connector types. The RF signal outputs via AC-coupled, differential CML RF connectors, which minimize signal noise and can provide high-speed data rates and require no external terminating resistors. Custom units with FC/APC connectors also available upon request; please contact Tech Support with inquiries.

The performance of each photoreceiver is factory tested, and the individualized test results are provided with each receiver. Please contact Tech Support if you would also like to receive a data file containing these test results.

Click to Enlarge

Internal Block Diagram Showing the Photodiode, Amplifier Stages,
Control Pins, and Differential RF Outputs

Click to Enlarge

The RX40AF photoreceiver features adjustable peaking (frequency response shape), which can be set through the Peaking Adjust pin outs (PKL and PKH). This graph illustrates one setting: Gain Control = 1.3 V, PKL = 0.0 V, and PKH = 2.7 V.
Item # Full
Fiber Type Bandwidth Wavelength
Responsivity Conversion
Gain (Max)b
Optical Return
Loss (Max)
Power (NEP)c
Dark Current
RX40AF info SMF-28 300 kHz - 40 GHz 1250 - 1650 nm 0.7 A/W 3500 V/W -28 dB 21 pW/√Hz 50 nA (Max)
  • All specifications are typical at 25 °C and 1550 nm unless otherwise noted.
  • Across External 50 Ω Load
  • The NEP is limited by the thermal noise of the combined internal and external load resistors.
Component Schematic
Click to Enlarge

Device Schematic

Operation Guide

Please reference the drawing to the right for connection options. Unpack the unit carefully making sure to take ESD precautions. For detailed operation procedures, refer to the individual product spec sheet by clicking the Support Docs icon (Docs Icon) for the specific item below.

  1. Mount the unit using the M2.5 x 0.45 mounting holes. It is possible to use M2 screws for mounting if bypassing the M2.5 threads in the feet is desired.
  2. Attach the GPPO® RF outputs of the unit to the measurement instrument using suitable cables or adapters. The measurement instrument must have a 50 Ω input and adequate bandwidth to resolve the high-speed signal from the detector. If only one output is used the other output must be terminated with a high quality 50 Ω termination.
  3. See datasheet for the pin out and detailed instructions to bias the device. It is critical that the power up and power down sequence is performed correctly:
    1. Power-Up Sequence: Photodiode First, Then Amplifier, Then Control Pins
    2. Power-Down Sequence: Control Pins First, Then Amplifier, Then Photodiode
  4. Couple the optical input signal to the photoreceiver via the FC/PC connector. Ensure the average input optical power does not exceed 10 dBm.
  5. The DC photocurrent can be monitored using a resistor in series with the bias pin and a voltmeter across the resistor. Make sure that the voltage drop across the resistor does not reduce the bias on the module below its operating voltage.

ESD Sensitive Components: Please note that the components inside the RX40AF module 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.

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.

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MX40B with cover removed
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 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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Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
RX40AF Support Documentation
RX40AFSingle Mode Photoreceiver Module, 1250 - 1650 nm, 300 kHz - 40 GHz, FC/PC
5-8 Days
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