Thorlabs Inc.
Visit the Balanced Amplified Photodetectors with Fast Monitor Output page for pricing and availability information

Balanced Amplified Photodetectors with Fast Monitor Output

  • Models Available with Bandwidths Up to 2.5 GHz
  • Noise Cancellation by Subtraction of 2 Input Signals
  • >20 dB Common Mode Rejection Ratio
  • Fast Monitor Outputs

PDB415A

Fixed Gain, 100 MHz, Si
Optical Inputs Shown

PDB450C

Switchable Gain, InGaAs
Optical Inputs Shown

PDB482C-AC

Fixed Gain, 2.5 GHz, InGaAs, AC Coupled
Electrical Outputs Shown

Hide Overview

OVERVIEW

Balanced Detector Selection Guide
Balanced Detectors with Fast Monitor Output
Large-Area Balanced Amplified Detectors
Suitable for OCT
Compact Balanced Amplified Detectors
Compact 5 GHz Balanced Detectors
OCT Balanced Detectors with Fast Monitor Output
Auto-Balanced Detector with Avalanche Photodiodes
Polarization-Dependent Balanced Detector

Typical Applications

  • Spectroscopy
  • Heterodyne Detection
    (See Doppler LIDAR Tab)
  • Optical Coherence Tomography OCT
  • Optical Delay Measurements
  • THz Detection
Balanced Detector with Fast Monitor Output
Bandwidth Available
Wavelength Ranges		 Fast Monitor
Output Bandwidth		 Gain
Switchable
(DC - 0.1, 0.3, 4,
45, or 150 MHz)		 320 to 1000 nm
or
800 - 1700 nm		 DC - 1 MHz Switchable
DC - 15 MHz Fixed
DC - 75 MHz
DC - 100 MHz
DC - 200 MHz
DC - 350 MHz
DC - 400 MHz Optimized for 1060 nm
(900 - 1400 nm Range)
or
Optimized for 1300 nm
(1200 - 1700 nm Range)		 DC - 3 MHz
DC - 500 MHz 800 - 1700 nm DC - 1 MHz
30 kHz - 1.0 GHz Optimized for 1060 nm
(900 - 1400 nm Range)		 DC - 3 MHz
30 kHz - 1.6 GHz Optimized for 1300 nm
(1200 - 1700 nm Range)		 DC - 3 MHz
1 MHz - 2.5 GHz Optimized for 1060 nm
(900 - 1400 nm Range)		 DC - 2.5 MHz
Coherent Detection using Balanced Photodetectors

Features

  • Four Wavelength Ranges Available
    • 320 - 1000 nm
    • 800 - 1700 nm
    • 900 - 1400 nm (Optimized for 1060 nm)
    • 1200 - 1700 nm (Optimized for 1300 nm)
  • >20 dB Common Mode Rejection Ratio
  • Fast Monitor Outputs
  • Choose a Si or InGaAs Detector
  • FC Fiber Inputs Available in All Versions
  • Free-Space Inputs Available on Some Detectors (See Below for Details)
  • Switchable Power Supply Included
  • Switchable Transimpedance Gain Version Available

These balanced photodetectors act as a balanced receiver by subtracting the two optical input signals from each other, resulting in the cancellation of common mode noise. This allows small changes in the signal path to be extracted from the interfering noise floor.

The detectors consist of two balanced photodiodes and an ultra-low-noise, high-speed transimpedance amplifier. The two photodiodes are matched to achieve an excellent common mode rejection ratio (CMRR), leading to better noise reduction. Please see the Operation tab for more details. All of these detectors incorporate three female SMA electrical ports for reduced noise. In addition to the RF-output from the transimpedance amplifier, the Monitor+ and Monitor- ports allow the response of each photodiode to be observed individually.

To block the CW component (the unmodulated part) of the optical input signal, an AC-coupled version of each detector is offered. Note that the PDB480C-AC, PDB481C-AC, and PDB482C-AC are only available AC coupled. This improves the ability to measure a comparably weak, frequency-modulated signal over a strong CW background signal that could saturate the amplifier. The lower cut-off frequency for the AC-coupled versions, with exception to the PDB480C-AC, PDB481C-AC, PDB482C-AC, and PDB835-AC, is guaranteed to be ≤100 Hz, but will typically be below 5 Hz.

Bandwidths up to 350 MHz
Detectors with bandwidths of DC - 350 MHz or lower are available with either Si or InGaAs photodiodes for the 320 - 1000 nm or 800 - 1700 nm range, respectively. The inputs on these detectors are not fiber coupled to the photodiodes and come with two removable FC input connectors, making them suitable for either free-space or fiber applications. Although the PDB465 and PDB435 detectors also contain non-fiber-coupled sensors, the FC/PC adapters at the inputs cannot be removed.

Housed in a shielded aluminum enclosure measuring 85 mm x 80 mm x 30 mm, these detectors are post mountable using the included adapter plate, which can be attached to the bottom or side of the housing with the included M2 screws.

Bandwidths of 400 MHz and Higher (Excluding PDB835 Series)
Detectors with bandwidths of DC - 400 MHz or higher other than PDB835 series detectors feature fiber-coupled photodiodes connected to FC/APC optical inputs with exactly length-matched SMF-28e+ or HI1060 fiber to achieve excellent CMRR values across the full detector bandwidth. All of these detectors incorporate InGaAs photodiodes and are optimized for either 1060 nm (900 - 1400 nm range) or 1300 nm (1200 - 1700 nm range). The fiber-coupled design suppresses line artifacts in the OCT image, which generally occur when detector coupling optics are used.

Our highest bandwidth balanced detectors (PDB480C-AC, PDB481C-AC, and PDB482C-AC) are offered in an AC version only. They offer bandwidths up to 2.5 GHz, leading to considerable speed improvements. The ultra-low-distortion output stage supports up to a 2 Vp-p A/D card input range, which, combined with the fiber-coupled design, improves the image quality for OCT applications considerably.

Housed in a shielded aluminum enclosure measuring 85 mm x 80 mm x 30 mm, these detectors are post mountable using the included adapter plate, which can be attached to the bottom or side of the housing with the included M2 screws.

PDB835 Series Ultra-Low-Noise, Artifact-Free Detectors (DC - 500 MHz)
The PDB835C and PDB35C-AC detectors feature free-space InGaAs photodiodes connected to FC/APC optical inputs for the 800 - 1700 nm range. Their transimpedance amplifiers feature ultra-low noise over their entire operating bandwidth (up to 500 MHz; see the Specs tab for details on the minimum NEP). These detectors feature FC/APC connectors which are individually aligned to the photodiode and achieve artifact-free operation. Each detector features a compact 76.7 mm x 60.0 mm x 20.0 mm housing with 8-32 (M4 x 0.7) combi-thread mounting holes on the top and bottom sides for universal mounting.

Power Supply
Each detector is powered by the included ±12 V DC power supply, for which a replacement is available below.

Thorlabs also offers Fiber-Based Interferometers, which feature an integrated balanced detector. If you are primarily interested in using our balanced detectors with OCT systems, a condensed list of detectors suitable for this application can be found here.


Hide Specs

SPECS

Item # PDB415A(-AC) PDB415C(-AC) PDB425A(-AC) PDB425C(-AC) PDB435A(-AC) PDB435C(-AC)
Detector Type Si/PIN InGaAs/PIN Si/PIN InGaAs/PIN Si/PIN InGaAs/PIN
Wavelength Range 320 - 1000 nm 800 - 1700 nm 320 - 1000 nm 800 - 1700 nm 320 - 1000 nm 800 - 1700 nm
Max Responsivity (Typical) 0.53 A/W 1.0 A/W 0.53 A/W 1.0 A/W 0.50 A/W 1.0 A/W
Active Detector Diameter 0.8 mm 0.3 mm 0.8 mm 0.3 mm 0.4 mm 0.15 mm
Bandwidth (3 dB) DC - 100 MHz
AC Coupled (-AC Suffix): 100 Hz - 100 MHz		 DC - 75 MHz
AC Coupled (-AC Suffix): 100 Hz - 75 MHz		 DC - 350 MHz
AC Coupled (-AC Suffix): 100 Hz - 350 MHz
Common Mode Rejection Ratio >25 dB >35 dB >20 dB
Transimpedance Gaina 50 x 103 V/A 250 x 103 V/A 10 x 103 V/A
Minimum NEPb 12.03 pW/Hz1/2
(DC - 100 MHz)		 6.99 pW/Hz1/2
(DC - 100 MHz)		 9.5 pW/Hz1/2
(DC - 75 MHz)		 5.2 pW/Hz1/2
(DC - 75 MHz)		 32.3 pW/Hz1/2
(DC - 350 MHz)		 15.28 pW/Hz1/2
(DC - 350 MHz)
RF Output
Conversion Gain RF Outputa,c 26.5 x 103 V/W 50 x 103 V/W 133 x 103 V/W 250 x 103 V/W 5 x 103 V/W 10 x 103 V/W
CW Saturation Power RF Output 135 µW @ 820 nm 72 µW @ 1550 nm 27 µW @ 820 nm 15 µW @ 1550 nm 720 µW @ 820 nm 360 µW @ 1550 nm
Impedance 50 Ω
Max Voltage Swing ±1.8 V for 50 Ω Load
±3.6 V for High-Impedance Load
DC Offset < ±3 mV
RF-Output Coupling DC or AC
Monitor Outputs
Conversion Gain Monitor Outputs 10 V/mW @ 820 nm 10 V/mW @ 1550 nm 10 V/mW @ 820 nm 10 V/mW @ 1550 nm 10 V/mW @ 820 nm 10 V/mW @ 1550 nm
Impedance 220 Ω
Max Voltage Swing 1.55 V for 50 Ω Load
10 V for High-Z Load
Bandwidth DC to 1 MHz
Voltage Noise <180 µVRMS
DC Offset < ±2 mV
General
Fiber Optical Inputsd FC/PC or FC/APC
(Removable)		 FC/PC or FC/APC
(Not Removable)
Photodiode Damage Threshold 20 mW
Electrical Outputs SMA (Qty. 3)
Dimensions 85 mm x 80 mm x 30 mm (3.35" x 3.15" x 1.18")
Weight 0.35 kg (without Power Supply)
Operating Temperature Rangee 0 to 40 °C
Storage Temperature Range -40 to 70 °C
Included Power Supplyf ±12 V @ 250 mA
(100/120/230 VAC, 50 - 60 Hz, Switchable)
  • Value is given for high-impedance load. For a 50 Ω load, divide the value by 2.
  • For more information on NEP, please see Thorlabs' Noise Equivalent Power White Paper.
  • Given at detector peak responsivity.
  • For PDB435C FC and PDB465C the FC adapter is NOT removable.
  • Non-condensing.
  • A replacement power supply is available below.
Item # PDB440A(-AC) PDB440C(-AC) PDB450A(-AC) PDB450C(-AC) PDB465A(-AC) PDB465C(-AC)
Detector Type Si/PIN InGaAs/PIN Si/PIN InGaAs/PIN Si/PIN InGaAs/PIN
Wavelength Range 320 - 1000 nm 800 - 1700 nm 320 - 1000 nm 800 - 1700 nm 320 - 1000 nm 800 - 1700 nm
Max Responsivity (Typical) 0.53 A/W 1.0 A/W 0.53 A/W 1.0 A/W 0.50 A/W 1.0 A/W
Active Detector Diameter 0.8 mm 0.3 mm 0.8 mm 0.3 mm 0.8 mm 0.15 mm
Bandwidth (3 dB) DC - 15 MHz
AC Coupled (-AC Suffix): 100 Hz - 15 MHz		 DC - 150, 45, 4, 0.3, 0.1 MHz
AC Coupled (-AC Suffix): 100 Hz - 150, 45, 4, 0.3, 0.1 MHz		 DC - 200 MHz
AC Coupled (-AC Suffix): 100 Hz - 200 MHz
Common Mode Rejection Ratio >35 dB >25 dB >25 dB
Transimpedance Gaina 51 x 103 V/A 103, 104, 105, 106, 107 V/A 30 x 103 V/A
Minimum NEPb 6.9 pW/Hz1/2
(DC - 15 MHz)		 3.9 pW/Hz1/2
(DC - 15 MHz)		 DC - 0.1 MHz: 1.4 pW/Hz1/2
DC - 0.3 MHz: 1.1 pW/Hz1/2
DC - 4.0 MHz: 3.3 pW/Hz1/2
DC - 45 MHz: 28.9 pW/Hz1/2
DC - 150 MHz: 123 pW/Hz1/2		 DC - 0.1 MHz: 0.7 pW/Hz1/2
DC - 0.3 MHz: 0.5 pW/Hz1/2
DC - 4.0 MHz: 1.55 pW/Hz1/2
DC - 45 MHz: 14.9 pW/Hz1/2
DC - 150 MHz: 68.6 pW/Hz1/2		 22.86 pW/Hz1/2
(DC - 200 MHz)		 8.52 pW/Hz1/2
(DC - 200 MHz)
RF Output
Conversion Gain RF Outputa,c 27 x 103 V/W 51 x 103 V/W 0.53 x 103 V/W,
0.53 x 104 V/W,
0.53 x 105 V/W,
0.53 x 106 V/W,
0.53 x 107 V/W		 103 V/W,
104 V/W,
105 V/W,
106 V/W,
107 V/W		 16 x 103 V/W 30 x 103 V/W
CW Saturation Power RF Output 130 µW @ 820 nm 70 µW @ 1550 nm 9 mW @ 820 nm 4.5 mW @ 1550 nm 225 µW @ 820 nm 120 µW @ 1550 nm
Impedance 50 Ω
Max Voltage Swing ±1.8 for 50 Ω Load
±3.6 V for High-Impedance Load		 ±4.6 V (103 to 106 Gain)a
±10 V (107 Gain)a		 ±1.8 for 50 Ω Load
±3.6 V for High-Impedance Load
DC Offset < ±3 mV < ±15 mV < ±3 mV
RF-Output Coupling DC or AC
Monitor Outputs
Conversion Gain Monitor Outputs 10 V/mW @ 820 nm 10 V/mW @ 1550 nm 10 V/mW @ 820 nm 10 V/mW @ 1550 nm 10 V/mW @ 820 nm 10 V/mW @ 1550 nm
Impedance 220 Ω
Max Voltage Swing 1.55 V for 50 Ω Load
10 V for High-Z Load
Bandwidth DC to 1 MHz
Voltage Noise <180 µVRMS
DC Offset < ±2 mV
General
Fiber Optical Inputsd FC/PC or FC/APC
(Removable)		 FC/PC or FC/APC
(Not Removable)
Photodiode Damage Threshold 20 mW
Electrical Outputs SMA (Qty. 3)
Dimensions 85 mm x 80 mm x 30 mm (3.35" x 3.15" x 1.18")
Weight 0.35 kg (without Power Supply)
Operating Temperature Rangee 0 to 40 °C
Storage Temperature Range -40 to 70 °C
Included Power Supplyf ±12 V @ 250 mA
(100/120/230 VAC, 50 - 60 Hz, Switchable)
  • Value is given for a high-impedance load. For a 50 Ω load, divide the value by 2.
  • For more information on NEP, please see Thorlabs' Noise Equivalent Power White Paper.
  • Given at detector peak responsivity.
  • For PDB435C FC and PDB465C the FC adapter is NOT removable.
  • Non-condensing.
  • A replacement power supply is available below.
Item # PDB470C(-AC)a PDB471C(-AC)a PDB480C-ACa PDB481C-ACa PDB482C-ACa PDB835C(-AC)a
Detector
Detector Type InGaAs/PIN
Optical Inputs FC/APC
Internal Coupling Fiber SMF-28e+ HI1060 SMF-28e+ HI1060 None
Coupling Loss <0.5 dB (<0.3 dB Typ.) <1.0 dB (<0.4 dB Typ.) <0.5 dB (<0.3 dB Typ.) <1.0 dB (<0.4 dB Typ.) N/A
Operating Wavelength Optimized for 1300 nm
(1200 - 1700 nm Range)		 Optimized for 1060 nm
(900 - 1400 nm Range)		 Optimized for 1300 nm
(1200 - 1700 nm Range)		 Optimized for 1060 nm
(900 - 1400 nm Range)		 800 - 1700 nm
Responsivity (Typical) 0.9 A/W @ 1550 nm 0.72 A/W @ 1060 nm 0.9 A/W @ 1550 nm 0.72 A/W @ 1060 nm 1.0 A/W @ 1550 nm
Active Detector Diameter 0.075 mm 0.080 mm 0.075 mm 0.08 mm
Optical Back Reflection <-40 dB N/A
Photodiode
Damage Threshold		 10 mW 5 mW 10 mW 5 mW 20 mW
RF OUTPUT
RF OUTPUT Bandwidth (3 dB) DC - 400 MHz
AC Coupled (-AC Suffix): 100 Hz - 400 MHz		 30 kHz - 1.6 GHz 30 kHz - 1.0 GHz 1 MHz - 2.5 GHz DC - 500 MHz
AC Coupled (-AC Suffix):
1 kHz - 500 MHz
Common Mode Rejection Ratio >25 dB (Typ. >30 dB) >20 dB (Typ. >25 dB) >25 dB
RF OUTPUT Transimpedance Gain 10 x 103 V/Ab 16 x 103 V/Ac 28 x 103 V/Ac 10 x 103 V/Ad
RF OUTPUT Conversion Gain 9 x 103 V/W
@ 1550 nmb		 7.2 x 103 V/W
@ 1060 nmb		 14.4 x 103 V/W
@ 1550 nmc		 11.5 x 103 V/W
@ 1060 nmc		 20 x 103 V/W
@ 1060 nmc		 10 x 103 V/W @ 1550 nmd,e
RF OUTPUT Power
at 1 dB Compressionc		 - +16.5 dBm Min
+18 dBm Typ.		 -
RF OUTPUT CW Saturation Power 420 µW @ 1550 nm 530 µW @ 1060 nm See Note Below 360 mW @ 1550 nm
RF OUTPUT Coupling DC or AC AC Coupling Only DC or AC
RF OUTPUT Impedance 50 Ω
Max Voltage Swing ±1.9 V for 50 Ω Load
±3.8 V for High-Z Load		 See Note Below ±1.8 V for 50 Ω Load;
±3.6 V (Linear Over 0 to 2.5 V)
for High-Z Load
Minimum NEPf 8 pW/Hz1/2
(DC to 100 MHz)		 9.3 pW/Hz1/2
(30 kHz to 100 MHz)		 9.0 pW/Hz1/2
(30 kHz to 100 MHz)		 12.0 pW/Hz1/2
(1 MHz to 100 MHz)		 6.5 pW/Hz1/2
(DC to 500 MHz)
Overall Output Voltage Noise <2.0 mVRMS <9 mVRMS <6.5 mVRMS <12 mVRMS <1.5 mVRMS
DC Offset N/A < ±5 mV
MONITOR Outputs
MONITOR Output Impedance 200 Ω
MONITOR Output Bandwidth (3 dB) DC - 3 MHz DC - 2.5 MHz DC - 1 MHz
MONITOR Output Conversion Gain,
High Z Loadb		 9 V/mW @ 1550 nm 7.2 V/mW @ 1060 nm 9 V/mW @ 1550 nm 7.2 V/mW @ 1060 nm 10 V/mW @ 1550 nme
MONITOR Output Voltage Swing
 10 V Max, High Z Load 1.5 V Max for 50 Ω Load
10 V Max (Linear Over 0 to 5 V)
for High-Z Load
Overall Output Voltage Noise <0.65 mVRMS <0.6 mVRMS
DC Offset < ±2 mV < ±5 mV
General
Electrical Outputs SMA
Included DC Power Supplyg ±12 V @ 250 mA
(100/120/230 VAC, 50 - 60 Hz, Switchable)
Operating Temperature Rangeh 0 °C to 40 °C
Storage Temperature Range -40 °C to 70 °C
Dimensions (W x H x D) 85 mm x 80 mm x 30 mm
(3.35" x 3.15" x 1.18")		 76.7 mm x 60.0 mm x 20.0 mm
(3.02" x 2.36" x 0.79")
Weight 0.35 kg 0.13 kg
  • All technical data are valid at 23 ± 5 °C and 45 ± 15% relative humidity (non-condensing).
  • Values for transimpedance and conversion gain are lossless gain values [i.e. losses introduced by the FC/APC connectors (typically 0.15 to 0.35 dB) are not considered].
  • For a 50 Ω load.
  • Value is given for high-impedance load. For a 50 Ω load, divide the value by 2.
  • Value is given at detector peak responsivity.
  • For more information on NEP, please see Thorlabs' Noise Equivalent Power White Paper.
  • A replacement power supply is available below.
  • Non-Condensing.

Note:
For the PDB480C-AC, PDB481C-AC, and PDB482C-AC detectors the RF output signal must not exceed the RF Output Power at 1 dB Compression, which is the point at which the amplified signal at 1 GHz is compressed by 1 dB. Above this value, the amplified signal will become non-linear and begin to saturate. The RF output voltage at this saturation point can be calculated using the following formula:

where R is the load impedance (50 Ω), P0 is defined as 1 mW, and L(dBm) is the power level in dBm. Using the specified RF Output Power at 1 dB Compression of 16.5 dBm, this yields the following "maximum" output voltage:


Hide Operation

OPERATION

Operation of Balanced Detectors with Bandwidths up to 500 MHz

Thorlabs' Balanced Amplified Photodetectors consist of two well-matched photodiodes and an ultra-low noise, high-speed transimpedance amplifier (TIA) that generates an output voltage (RF OUTPUT) proportional to the difference between the photocurrents in the two photodiodes (i.e., the two optical input signals). Additionally, the unit has two fast monitor outputs (MONITOR+ and MONITOR-) to observe the optical input power levels on each photodiode separately. These outputs are low frequency outputs and cannot be used to measure an RF modulation on the signal. The block diagram applies to our balanced detectors with bandwidths up to 500 MHz.

Balanced receiver

Operation of the PDB480C-AC, PDB481C-AC, and PDB482C-AC Balanced Detectors

The PDB48xC-AC Balanced Amplified Photodetectors use the same basic operating principles as described above and have the following additional features. The TIA's ultra-low distortion output stage supports up to a 2 Vp-p A/D card input range. The two fast monitor outputs can be used to measure not only the individual optical input power levels, but also low frequency modulated signals up to 3 MHz (Item #s PDB480C-AC and PDB481C-AC) or 2.5 MHz (Item # PDB482C-AC). To enable the much higher frequency of these detectors, the photodiodes are connected to the inputs with length-matched fibers, only AC-coupled versions are offered, and capacitors are added to the circuit (as shown below).

Balanced receiver


Hide Pin Diagrams

PIN DIAGRAMS

Pin Diagrams for Balanced Amplified Photodetectors

Monitor +/-

SMA Female

BNC Female

Maximum Voltage is +10 V for Hi-Z & +1.5 V into 50 Ω loads.

RF Output

SMA Female

BNC Female

For the PDB415, PDB425, PDB440, PDB465, and PDB835 photodetectors, the maximum RF OUTPUT voltage is ±3.6 V for Hi-Z & ±1.8 V into 50 Ω loads.

The RF OUTPUT CW saturation power is 420 µW @ 1550 nm and 530 µW at 1060 nm for the PDB470C and PDB471C, respectively.

For the PDB48xC-AC photodetectors, the RF OUTPUT Power at 1 dB compression into 50 Ω loads is +16.5 dBm (Min), +18 dBm (Typical)

PDB Male (Power Cables)

Pinout for PDA Power Cable

PDB Female (Photodetector)

Pinout for PDA Power Connector


Hide Doppler LIDAR

DOPPLER LIDAR


Click to Enlarge
Figure 1. Block Diagram for Thorlabs' Balanced Detectors up to 15 MHz

Application Idea: Doppler LIDAR with Balanced Detector

We demonstrate how to build a Doppler LIDAR (Light Detection and Ranging) system with readily available components manufactured by Thorlabs. The main component is our high-gain balanced photodetector, Item # PDB440C. Balanced detectors are commonly used in applications with high noise levels, which lead to small Signal-to-Noise ratios (SNR).

LIDAR is an ideal application for balanced detectors because they offer common-mode rejection and the usage of both output arms from the 50/50 coupler (described below), which together improve the SNR. Common-mode rejection reduces common-mode noise (for PDB440C, by >25 dB), while using both outputs from the coupler, instead of only one, results in higher signal levels of 3 dB.

The balanced detector consists of two well-matched photodiodes and an ultra-low noise, high-speed transimpedance amplifier (TIA) that generates an output voltage (RF OUTPUT) proportional to the difference between the photocurrents in the two photodiodes.


Click to Enlarge
Figure 2. Generation of a beat frequency (left) and principle of the Doppler effect (right).

Theory of Doppler LIDAR

The optical frequency of electromagnetic waves is shifted when reflected from an object in motion. This phenomenon is generally known as the Doppler effect, or, equivalently, as a Doppler shift. When the detector is at a fixed position and the object is moving towards the detector with velocity v, then the Doppler shift Δf can be described as:

Where:

c: Speed of Light (m/s)

f0: Optical Frequency Emitted by Light Source (Hz)

f1: Optical Frequency of Light Reflected from Object (Hz)

In the typical wavelength ranges of our balanced detectors, optical frequencies lie in the THz regime, which are too fast to record directly with photodiodes. On the other hand, consider the following example:

This example shows that for velocities < 0.75 m/s and an optical frequency of 200 THz, which corresponds to a 1500 nm wavelength, the Doppler shift Δf will be in the kHz regime, meaning that the beat frequency from the reference signal (f0) and the Doppler shifted signal (f1) is detectable with standard photodiodes. The detection of two superimposed signals of different frequencies is known as heterodyne detection.

Setup and Principle

The basic components are a fiber-coupled light source with driver, a fiber coupler with a 99/1 coupling ratio, a fiber coupler with a 50/50 coupling ratio, a fiber circulator, a fiber collimator, a balanced detector, an oscilloscope with Fast Fourier Transform capability, and an object moving with velocity v.


Click to Enlarge
Figure 3. Doppler LIDAR Setup on a Breadboard
Components Details
1 Collimator F810APC-1550
2 Light Source LP1550-SAD2 DFB Laser with Center Wavelength of 1550.1 nm
3 LD & TEC Driver CLD1010LP Compact Laser Diode/Temperature Controller
4 Fiber Coupler (99/1) TN1550R1A2
5 Fiber Coupler (50/50) TN1550R5A2
6 Fiber Circulator 6015-3-APC
7 Detector PDB440C Balanced Photodetector (CMRR > 35 dB; Gain 51 x 103 V/W)
Analyzer Standard Oscilloscope (with 500 kHz Fast Fourier Transform) or Spectrum Analyzer
Object EDU-VS1/M Viewing Screen, Mounted on DDSM100/M Linear Stage

Light emitted by the LP1550-SAD2 DFB Laser is split by a 99/1 fiber coupler. The 99% arm propagates to the fiber circulator, which directs the light to the fiber collimator for coupling into free space. The collimated beam points towards a moving object with velocity v, and the reflected light is coupled into the fiber. On the way back, the circulator guides the light to the 50/50 fiber coupler, whose other input is the 1% arm of the 99/1 coupler. Both outputs from the 50/50 coupler therefore contain mixed optical signals, which are detected by the PDB440C balanced detector.


Click to Enlarge
Figure 4. Schematic Setup for Doppler LIDAR

Measurement and Results

The linear stage is set to a velocity of 250 mm/s. The resulting signal is a sharp peak with an SNR of more than 10 dB. The velocity is calculated as follows:

The accuracy of the velocity of the linear translation stage has an observed deviation of 9 mm/s (3.5%), which is within the expected range of the configuration.

The object is placed on the DDSM100/M linear translation stage, which has a 100 mm travel range. While moving the object, the velocity is non-constant for an unknown distance, because the linear stage has limited acceleration. Thus, the signal's frequency varies while the object travels from 0 mm to 100 mm. The time duration for one measurement at the analyzer, which is an oscilloscope with fast Fourier transform capability, is some tens of milliseconds, so we do not observe continuous movement of the signal, but rather jumps with non-constant intervals. Therefore, we used the maximum peak hold function to evaluate the correlation of the frequency to the maximum velocity of the object. This function captures the peak with highest amplitude during one frequency scan.

This application idea shows a generic configuration and demonstration of a Doppler LIDAR with Thorlabs components. Please contact techsupport@thorlabs.com for questions and comments regarding the application idea or your application.


Click to Enlarge
Figure 6. Measurement of the frequency Δf in FFT mode with the oscilloscope max peak hold function.

Click to Enlarge
Figure 5. Measurement of a 333.786 kHz beat frequency Δf in
FFT mode.

Hide Switchable Gain with Fast Monitor Output

Switchable Gain with Fast Monitor Output

Specificationsa
Item # PDB450A(-AC) PDB450C(-AC)
Detector Type Si/PIN InGaAs/PIN
Wavelength Range 320 - 1000 nm 800 - 1700 nm
Max Responsivity (Typical) 0.53 A/W 1.0 A/W
Active Detector Diameter 0.8 mm 0.3 mm
Bandwidth (3 dB) DC - 150, 45, 4, 0.3, 0.1 MHz
AC Coupled (-AC Suffix): 100 Hz - 150, 45, 4, 0.3, 0.1 MHz
Common Mode
Rejection Ratio		 >25 dB
Transimpedance Gainb 103, 104, 105, 106, 107 V/A
Minimum NEP DC - 0.1 MHz: 1.4 pW/Hz1/2
DC - 0.3 MHz: 1.1 pW/Hz1/2
DC - 4.0 MHz: 3.3 pW/Hz1/2
DC - 45 MHz: 28.9 pW/Hz1/2
DC - 150 MHz: 123 pW/Hz1/2		 DC - 0.1 MHz: 0.7 pW/Hz1/2
DC - 0.3 MHz: 0.5 pW/Hz1/2
DC - 4.0 MHz: 1.55 pW/Hz1/2
DC - 45 MHz: 14.9 pW/Hz1/2
DC - 150 MHz: 68.6 pW/Hz1/2
Optical Inputs FC/PC or FC/APC Compatible (Removable Adapter)
Monitor Output Bandwidth DC - 1 MHz
  • For a full list of specifications, please see the Specs tab above.
  • Transimpedance Gain is reduced by a factor of two for 50 Ω loads.
Responsitivity of PDB450 Balanced Detectors
Click to Enlarge

Part Number
Description
Price
Availability
PDB450A
Customer Inspired! Switchable Gain Balanced Amp. Photodetector, Si, 320 - 1000 nm
$1,778.88
Today
PDB450A-AC
Switchable Gain Balanced Amp. Photodetector, Si, 320 - 1000 nm, AC Coupled
$1,778.88
Today
PDB450C
Switchable Gain Balanced Amp. Photodetector, InGaAs, 800 - 1700 nm
$1,901.23
7-10 Days
PDB450C-AC
Switchable Gain Balanced Amp. Photodetector, InGaAs, 800 - 1700 nm, AC Coupled
$1,901.23
Lead Time

Hide Bandwidth: DC to 15 MHz with Fast Monitor Output

Bandwidth: DC to 15 MHz with Fast Monitor Output

Specificationsa
Item # PDB440A(-AC) PDB440C(-AC)
Detector Type Si/PIN InGaAs/PIN
Wavelength Range 320 - 1000 nm 800 - 1700 nm
Max Responsivity (Typical) 0.53 A/W 1.0 A/W
Active Detector Diameter 0.8 mm 0.3 mm
Bandwidth (3 dB) DC - 15 MHz
AC Coupled (-AC Suffix): 100 Hz - 15 MHz
Common Mode Rejection Ratio >35 dB
Transimpedance Gainb 51 x 103 V/A
Minimum NEP 6.9 pW/Hz1/2
(DC - 15 MHz)		 3.9 pW/Hz1/2
(DC - 15 MHz)
Optical Inputs FC/PC or FC/APC Compatible (Removable Adapter)
Monitor Output Bandwidth DC - 1 MHz
  • For a full list of specifications, please see the Specs tab above.
  • Transimpedance Gain is reduced by a factor of two for 50 Ω loads.
Responsitivity of PDB440 Balanced Detectors
Click to Enlarge

Part Number
Description
Price
Availability
PDB440A
Fixed Gain Balanced Amp. Photodetector, 15 MHz, Si, 320 - 1000 nm
$1,693.71
Lead Time
PDB440A-AC
Fixed Gain Balanced Amp. Photodetector, 15 MHz, Si, 320 - 1000 nm, AC Coupled
$1,693.71
7-10 Days
PDB440C
Fixed Gain Balanced Amp. Photodetector, 15 MHz, InGaAs, 800 - 1700 nm
$1,790.89
Today
PDB440C-AC
Fixed Gain Balanced Amp. Photodetector, 15 MHz, InGaAs, 800 - 1700 nm, AC Coupled
$1,790.89
7-10 Days

Hide Bandwidth: DC to 75 MHz with Fast Monitor Output

Bandwidth: DC to 75 MHz with Fast Monitor Output

Specificationsa
Item # PDB425A(-AC) PDB425C(-AC)
Detector Type Si/PIN InGaAs/PIN
Wavelength Range 320 - 1000 nm 800 - 1700 nm
Max Responsivity (Typical) 0.53 A/W 1.0 A/W
Active Detector Diameter 0.8 mm 0.3 mm
Bandwidth (3 dB) DC - 75 MHz
AC Coupled (-AC Suffix): 100 Hz - 75 MHz
Common Mode Rejection Ratio >35 dB
Transimpedance Gainb 250 x 103 V/A
Minimum NEP 9.5 pW/Hz1/2
(DC - 75 MHz)		 5.2 pW/Hz1/2
(DC - 75 MHz)
Optical Inputs FC/PC or FC/APC Compatible (Removable Adapter)
Monitor Output Bandwidth DC - 1 MHz
  • For a full list of specifications, please see the Specs tab above.
  • Transimpedance Gain is reduced by a factor of two for 50 Ω loads.
Responsitivity of PDB420 Balanced Detectors
Click to Enlarge

Part Number
Description
Price
Availability
PDB425A
Fixed Gain Balanced Amp. Photodetector, 75 MHz, Si, 320 - 1000 nm
$1,558.16
Today
PDB425A-AC
Fixed Gain Balanced Amp. Photodetector, 75 MHz, Si, 320 - 1000 nm, AC Coupled
$1,558.16
Today
PDB425C
Fixed Gain Balanced Amp. Photodetector, 75 MHz, InGaAs, 800 - 1700 nm
$1,668.52
Lead Time
PDB425C-AC
Fixed Gain Balanced Amp. Photodetector, 75 MHz, InGaAs, 800 - 1700 nm, AC Coupled
$1,668.52
Today

Hide Bandwidth: DC to 100 MHz with Fast Monitor Output

Bandwidth: DC to 100 MHz with Fast Monitor Output

Specificationsa
Item # PDB415A(-AC) PDB415C(-AC)
Detector Type Si/PIN InGaAs/PIN
Wavelength Range 320 - 1000 nm 800 - 1700 nm
Max Responsivity (Typical) 0.53 A/W 1.0 A/W
Active Detector Diameter 0.8 mm 0.3 mm
Bandwidth (3 dB) DC - 100 MHz
AC Coupled (-AC Suffix): 100 Hz - 100 MHz
Common Mode Rejection Ratio >25 dB
Transimpedance Gainb 50 x 103 V/A
Minimum NEP 12.03 pW/Hz1/2
(DC - 100 MHz)		 6.99 pW/Hz1/2
(DC - 100 MHz)
Optical Inputs FC/PC or FC/APC Compatible (Removable Adapter)
Monitor Output Bandwidth DC - 1 MHz
  • For a full list of specifications, please see the Specs tab above.
  • Transimpedance Gain is reduced by a factor of two for 50 Ω loads.
Responsitivity of PDB410 Balanced Detectors
Click to Enlarge

Part Number
Description
Price
Availability
PDB415A
Fixed Gain Balanced Amp. Photodetector, 100 MHz, Si, 320 - 1000 nm
$1,398.63
7-10 Days
PDB415A-AC
Fixed Gain Balanced Amp. Photodetector, 100 MHz, Si, 320 - 1000 nm, AC Coupled
$1,398.63
Today
PDB415C
Fixed Gain Balanced Amp. Photodetector, 100 MHz, InGaAs, 800 - 1700 nm
$1,471.80
7-10 Days
PDB415C-AC
Fixed Gain Balanced Amp. Photodetector, 100 MHz, InGaAs, 800 - 1700 nm, AC Coupled
$1,471.80
Lead Time

Hide Bandwidth: DC to 200 MHz with Fast Monitor Output

Bandwidth: DC to 200 MHz with Fast Monitor Output

Specificationsa
Item # PDB465A(-AC) PDB465C(-AC)
Detector Type Si/PIN InGaAs/PIN
Wavelength Range 320 - 1000 nm 800 - 1700 nm
Max Responsivity (Typ.) 0.50 A/W 1.0 A/W
Active Detector Diameter 0.8 mm 0.15 mm
Bandwidth (3 dB) DC - 200 MHz
AC Coupled (-AC Suffix): 100 Hz - 200 MHz
Common Mode
Rejection Ratio		 >25 dB
Transimpedance Gainb 30 x 103 V/A
Minimum NEP 22.86 pW/Hz1/2
(DC - 200 MHz)		 8.52 pW/Hz1/2
(DC - 200 MHz)
Optical Inputs FC/PC or FC/APC Compatible
(Removable Adapter)		 FC/PC or FC/APC Compatible
(Adapter is not Removable)
Monitor Output Bandwidth DC - 1 MHz
  • For a full list of specifications, please see the Specs tab above.
  • Transimpedance Gain is reduced by a factor of two for 50 Ω loads.
Responsitivity of PDB460 Balanced Detectors
Click to Enlarge

Part Number
Description
Price
Availability
PDB465A
Fixed Gain Balanced Amp. Photodetector, 200 MHz, Si, 320 - 1000 nm
$1,717.70
Lead Time
PDB465A-AC
Fixed Gain Balanced Amp. Photodetector, 200 MHz, Si, 320 - 1000 nm, AC Coupled
$1,717.70
7-10 Days
PDB465C
Fixed Gain Balanced Amp. Photodetector, 200 MHz, InGaAs, 800 - 1700 nm
$1,693.71
Today
PDB465C-AC
Fixed Gain Balanced Amp. Photodetector, 200 MHz, InGaAs, 800 - 1700 nm, AC Coupled
$1,693.71
Today

Hide Bandwidth: DC to 350 MHz with Fast Monitor Output

Bandwidth: DC to 350 MHz with Fast Monitor Output

Specificationsa
Item # PDB435A(-AC) PDB435C(-AC)
Detector Type Si/PIN InGaAs/PIN
Wavelength Range 320 - 1000 nm 800 - 1700 nm
Max Responsivity (Typ.) 0.50 A/W 1.0 A/W
Active Detector Diameter 0.4 mm 0.15 mm
Bandwidth (3 dB) DC - 350 MHz
AC Coupled (-AC Suffix): 100 Hz - 350 MHz
Common Mode
Rejection Ratio		 >20 dB
Transimpedance Gainb 10 x 103 V/A
Minimum NEP 32.3 pW/Hz1/2
(DC - 350 MHz)		 15.28 pW/Hz1/2
(DC - 350 MHz)
Optical Inputs FC/PC or FC/APC Compatible
(Removable Adapter)		 FC/PC or FC/APC Compatible
(Adapter is not Removable)
Monitor Output Bandwidth DC - 1 MHz
  • For a full list of specifications, please see the Specs tab above.
  • Transimpedance Gain is reduced by a factor of two for 50 Ω loads.
Responsitivity of PDB430 Balanced Detectors
Click to Enlarge

Part Number
Description
Price
Availability
PDB435A
Fixed Gain Balanced Amp. Photodetector, 350 MHz, Si, 320 - 1000 nm
$1,778.88
Today
PDB435A-AC
Fixed Gain Balanced Amp. Photodetector, 350 MHz, Si, 320 - 1000 nm, AC Coupled
$1,778.88
Today
PDB435C
Fixed Gain Balanced Amp. Photodetector, 350 MHz, InGaAs, 800 - 1700 nm
$1,901.23
Today
PDB435C-AC
Fixed Gain Balanced Amp. Photodetector, 350 MHz, InGaAs, 800 - 1700 nm, AC Coupled
$1,901.23
Today

Hide Bandwidth: DC to 400 MHz with Fast Monitor Output

Bandwidth: DC to 400 MHz with Fast Monitor Output

Specificationsa
Item # PDB471C(-AC) PDB470C(-AC)
Operating Wavelength Optimized for 1060 nm
(900 - 1400 nm Range)		 Optimized for 1300 nm
(1200 - 1700 nm Range)
Detector Type InGaAs/PIN
Internal Coupling Fiber HI1060 SMF-28e+
Responsivity (Typical) 0.72 A/W @ 1060 nm 0.9 A/W @ 1550 nm
Active Detector Diameter 0.080 mm 0.075 mm
Bandwidth (3 dB) DC - 400 MHz
AC Coupled (-AC Suffix): 100 Hz - 400 MHz
Common Mode Rejection Ratio >25 dB
(Typ. >30 dB)
Transimpedance Gainb 10 x 103 V/A
Minimum NEP 8 pW/Hz1/2 (DC to 100 MHz)
Optical Inputs FC/APC
Monitor Output Bandwidth DC - 3 MHz
  • For a full list of specifications, please see the Specs tab above.
  • Value for transimpedance gain is a lossless gain value [i.e., losses introduced by FC/APC connectors (typically 0.15 to 0.35 dB) are not considered].

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

Responsitivity of the PDB470C-AC and PDB471C-AC Balanced Detectors
Click to Enlarge
The two vertical lines mark 1060 nm (red) and 1300 nm (blue). The shaded regions indicate the specified wavelength range for each detector.

Part Number
Description
Price
Availability
PDB471C
Fiber-Coupled Balanced Amp. Photodetector, 400 MHz, InGaAs, 1060 nm
$2,147.13
7-10 Days
PDB471C-AC
Fiber-Coupled Balanced Amp. Photodetector, 400 MHz, InGaAs, 1060 nm, AC Coupled
$2,147.13
7-10 Days
PDB470C
Customer Inspired! Fiber-Coupled Balanced Amp. Photodetector, 400 MHz, InGaAs, 1300 nm
$2,024.77
7-10 Days
PDB470C-AC
Customer Inspired! Fiber-Coupled Balanced Amp. Photodetector, 400 MHz, InGaAs, 1300 nm, AC Coupled
$2,024.77
Today

Hide Bandwidth: DC to 500 MHz with Fast Monitor Output

Bandwidth: DC to 500 MHz with Fast Monitor Output

Specificationsa
Item # PDB835C(-AC)
Detector Type InGaAs/PIN
Wavelength Range 800 - 1700 nm
Max Responsivity (Typical) 1.0 A/W @ 1550 nm
Active Detector Diameter 0.08 mm
Bandwidth (3 dB) DC - 500 MHz
AC Coupled (-AC Suffix): 1 kHz - 500 MHz
Common Mode Rejection Ratio >25 dB
Transimpedance Gainb 10 x 103 V/A
Minimum NEP 6.5 pW/Hz1/2 (DC to 500 MHz)
Optical Inputs FC/APC
Monitor Output Bandwidth DC - 1 MHz
  • For a full list of specifications, please see the Specs tab above.
  • Transimpedance Gain is reduced by a factor of two for 50 Ω loads.

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

Responsitivity of PDB835 Balanced Detectors
Click to Enlarge

Part Number
Description
Price
Availability
PDB835C
Customer Inspired! Fixed Gain Balanced Amp. Photodetector, 500 MHz, InGaAs, 800 - 1700 nm
$1,989.00
Today
PDB835C-AC
Customer Inspired! Fixed Gain Balanced Amp. Photodetector, 500 MHz, InGaAs, 800 - 1700 nm, AC Coupled
$1,989.00
Lead Time

Hide Bandwidth: 30 kHz to 1 GHz or 1.6 GHz with Fast Monitor Output

Bandwidth: 30 kHz to 1 GHz or 1.6 GHz with Fast Monitor Output

Specificationsa
Item # PDB481C-AC PDB480C-AC
Operating Wavelength Optimized for 1060 nm
(900 - 1400 nm Range)		 Optimized for 1300 nm
(1200 - 1700 nm Range)
Detector Type InGaAs/PIN
Internal Coupling Fiber HI1060 SMF-28e+
Responsivity (Typical) 0.72 A/W @ 1060 nm 0.9 A/W @ 1550 nm
Active Detector Diameter 0.080 mm 0.075 mm
Bandwidth (3 dB) 30 kHz - 1.0 GHz 30 kHz - 1.6 GHz
Common Mode
Rejection Ratio		 >25 dB
(Typ. >30 dB)
Transimpedance Gainb 16 x 103 V/A
Minimum NEP 9.0 pW/Hz1/2
(30 kHz to 100 MHz)		 9.3 pW/Hz1/2
(30 kHz to 100 MHz)
Optical Inputs FC/APC
Monitor Output Bandwidth DC - 3 MHz
  • For a full list of specifications, please see the Specs tab above.
  • For a 50 Ω load.

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

Responsitivity of the PDB480C-AC and PDB481C-AC Balanced Detectors
Click to Enlarge
The two vertical lines mark 1060 nm (red) and 1300 nm (blue). The shaded regions indicate the operating wavelength range for each detector.

Part Number
Description
Price
Availability
PDB481C-AC
Fiber-Coupled Balanced Amp. Photodetector, 1.0 GHz, InGaAs, 1060 nm, AC Coupled
$2,147.13
Today
PDB480C-AC
Fiber Coupled Balanced Amp. Photodetector, 1.6 GHz, InGaAs, 1300 nm, AC Coupled
$2,036.78
Lead Time

Hide Bandwidth: 1 MHz to 2.5 GHz with Fast Monitor Output

Bandwidth: 1 MHz to 2.5 GHz with Fast Monitor Output

Specificationsa
Item # PDB482C-AC
Operating Wavelength Optimized for 1060 nm
(900 - 1400 nm Range)
Detector Type InGaAs/PIN
Internal Coupling Fiber HI1060
Responsivity (Typical) 0.72 A/W @ 1060 nm
Active Detector Diameter 0.080 mm
Bandwidth (3 dB) 1 MHz - 2.5 GHz
Common Mode Rejection Ratio >20 dB
(>25 dB Typ.)
Transimpedance Gainb 28 x 103 V/A
Minimum NEP 12.0 pW/Hz1/2
(1 MHz to 100 MHz)
Optical Inputs FC/APC
Monitor Output Bandwidth DC - 2.5 MHz
  • For a full list of specifications, please see the Specs tab above.
  • For a 50 Ω load.

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

Responsitivity of the PDB482C-AC Balanced Detector
Click to Enlarge
The vertical line marks the detector's optimized wavelength (1060 nm) while the shaded region indicates the operating wavelength range.

Part Number
Description
Price
Availability
PDB482C-AC
Fiber-Coupled Balanced Amp. Photodetector, 2.5 GHz, InGaAs, 1060 nm, AC Coupled
$2,147.13
Today

Hide ±12 VDC Regulated Linear Power Supply

±12 VDC Regulated Linear Power Supply

  • Replacement Power Supply for the Balanced Amplified Photodetectors Sold Above
  • ±12 VDC Power Output
  • Current Limit Enabling Short Circuit and Overload Protection
  • On/Off Switch with LED Indicator
  • Switchable AC Input Voltage (100, 120, or 230 VAC)
  • 2 m (6.6 ft) Cable with LUMBERG RSMV3 Male Connector
  • UL and CE Compliant

The LDS12B ±12 VDC Regulated Linear Power Supply is intended as a replacement for the supply included with our PDB line of balanced photodetectors sold on this page. The cord has three pins: one for ground, one for +12 V, and one for -12 V (see diagram above). This power supply ships with a location-specific power cord. This power supply can also be used with the PDA series of amplified photodetectors, PMM series of photomultiplier modules, APD series of avalanche photodetectors, and the FSAC autocorrelator for femtosecond lasers.


Part Number
Description
Price
Availability
LDS12B
±12 VDC Regulated Linear Power Supply, 6 W, 100/120/230 VAC
$93.55
Today