OCT Balanced Detectors with Fast Monitor Output

Models Available with Bandwidths up to 2.5 GHz
Wavelengths Covering the 320 to 1700 nm Range
>20 dB Common Mode Rejection Ratio
Fast Monitor Outputs

PDB415C

Fixed Gain, 100 MHz, Si
Optical Inputs Shown

PDB482C-AC

Fixed Gain, 2.5 GHz, InGaAs, AC Coupled
Optical Inputs Shown

PDB440C

Fixed Gain, 15 MHz, InGaAs
Electrical Outputs Shown

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Overview
Specs
Operation
Pin Diagrams
Feedback

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

OCT Balanced Detectors with Fast Monitor Output
Wavelength	Bandwidths Available	Fast Monitor Output Bandwidth
320 - 1000 nm	DC - 15 MHz DC - 75 MHz DC - 100 MHz DC - 200 MHz	DC - 1 MHz
800 - 1700 nm	DC - 15 MHz DC - 75 MHz DC - 100 MHz DC - 200 MHz	DC - 1 MHz
Optimized for 1060 nm (900 - 1400 nm Range)	DC - 400 MHz 30 kHz - 1.0 GHz	DC - 3 MHz
Optimized for 1060 nm (900 - 1400 nm Range)	1 MHz - 2.5 GHz	DC - 2.5 MHz
Optimized for 1300 nm (1200 - 1700 nm Range)	DC - 400 MHz 30 kHz - 1.6 GHz	DC - 3 MHz

Features

Bandwidths up to 2.5 GHz Available
Four Wavelength Options
- 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
All Versions Available with FC Fiber Inputs
Free Space Inputs on Some Detectors (See Below for Details)
Switchable Power Supply Included

These balanced amplified photodetectors are designed specifically for OCT applications. They 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.

Bandwidths of DC - 200 MHz or Lower
Detectors with bandwidths of DC - 200 MHz or lower are available with either Si photodiodes for the 320 - 1000 nm range or InGaAs photodiodes for the 800 - 1700 nm range. Choose from four bandwidths: DC - 15 MHz, DC - 75 MHz, DC - 100 MHz, or DC - 200 MHz. The inputs on these detectors are not fiber coupled to the photodiodes. Detectors with bandwidths of DC - 100 MHz or lower come with two removable FC input connectors, making them suitable for either free space or fiber applications. The DC - 200 MHz bandwidth detectors also have FC/PC connectors at the inputs, but they cannot be removed.

Bandwidths of DC - 400 MHz or Higher
Detectors with bandwidths of DC - 400 MHz or higher feature fiber-coupled InGaAs 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. The fiber-coupled design suppresses line artifacts in the OCT image, which generally occur when detector coupling optics are used. The combination of fiber and photodiodes was chosen to optimize these detectors for either 1060 nm (900 - 1400 nm range) or 1300 nm (1200 - 1700 nm range).

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

Packaging/Power Supply
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. A ±12 V linear power supply that supports input voltages of 100, 120, and 230 VAC is included with each amplified photodetector. Replacement power supplies are available separately below.

A complete list of all of Thorlabs' balanced amplified photodetectors with fast monitor output can be found here. Alternatively, we also offer an APD-based auto-balanced detector with an exceptionally low noise floor suitable for OCT applications with low signal in the sample arm. Thorlabs also offers Fiber-Based Interferometers, which feature an integrated balanced detector.

Item #	PDB415A	PDB415C	PDB425A	PDB425C	PDB440A	PDB440C	PDB465A	PDB465C
Detector Type	Si/PIN	InGaAs/PIN	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	320 - 1000 nm	800 - 1700 nm
Typical Max Responsivity	0.53 A/W	1.0 A/W	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	0.3 mm	0.8 mm	0.15 mm
Bandwidth (3 dB)	DC - 100 MHz		DC - 75 MHz		DC - 15 MHz		DC - 200 MHz
Common Mode Rejection Ratio	>25 dB		>35 dB		>35 dB		<25 dB
Transimpedance Gain^a	50 x 10³ V/A		250 x 10³ V/A		51 x 10³ V/A		30 x 10³ V/A
Minimum NEP^b	12.03 pW/Hz^1/2 (DC - 100 MHz)	6.99 pW/Hz^1/2 (DC - 100 MHz)	9.5 pW/Hz^1/2(DC - 75 MHz)	5.2 pW/Hz^1/2 (DC - 75 MHz)	6.9 pW/Hz^1/2 (DC - 15 MHz)	3.9 pW/Hz^1/2(DC - 15 MHz)	22.86 pW/Hz^1/2 (DC - 200 MHz)	8.52 pW/Hz^1/2 (DC - 200 MHz)
RF Output
RF Output Conversion Gain^a,c	26.5 x 10³ V/W	50 x 10³ V/W	133 x 10³ V/W	250 x 10³ V/W	27 x 10³ V/W	51 x 10³ V/W	16 x 10³ V/W	30 x 10³ V/W
CW Saturation Power	135 µW @ 820 nm	72 µW @ 1550 nm	27 µW @ 820 nm	15 µW @ 1550 nm	130 µW @ 820 nm	70 µW @ 1550 nm	225 µW @ 820 nm	120 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^d
Monitor Outputs
Monitor Output Conversion Gain	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	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-Impedance Load
Bandwidth	DC to 1 MHz
Voltage Noise	<180 µV_RMS
DC Offset	< ±2 mV
General
Fiber Optical Inputs^e	FC/PC or FC/APC (Removable)					FC/PC or FC/APC (Not Removable)	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 Range^f	0 to 40 °C
Storage Temperature Range	-40 to 70 °C
Included Power Supply^g	±12 V @ 200 mA 115/230 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.
AC-coupled versions of each detector are also available here. AC coupled variants block the CW component (the unmodulated part) of the optical input signal. This improves the ability to measure a comparably weak, frequency-modulated signal over a strong CW background signal that could saturate the amplifier.
For PDB435C and PDB465C the FC adapter is NOT removable.
Non-condensing.
A replacement power supply that support input voltages of 100, 120, and 230 VAC is available below.

Item #	PDB470C^a	PDB471C^a	PDB480C-AC^a	PDB481C-AC^a	PDB482C-AC^a
Detector
Detector Type	InGaAs/PIN
Optical Inputs	FC/APC
Internal Coupling Fiber	SMF-28e+	HI1060	SMF-28e+	HI1060
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.)
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)
Responsivity (Typical)	0.9 A/W @ 1300 nm	0.72 A/W @ 1060 nm	0.9 A/W @ 1300 nm	0.72 A/W @ 1060 nm
Active Detector Diameter	0.075 mm	0.080 mm	0.075 mm	0.080 mm
Optical Back Reflection	<-40 dB
Photodiode Damage Threshold	10 mW	5 mW	10 mW	5 mW
RF OUTPUT
RF OUTPUT Bandwidth (3 dB)	DC - 400 MHz		30 kHz - 1.6 GHz	30 kHz - 1.0 GHz	1 MHz - 2.5 GHz
Common Mode Rejection Ratio	>25 dB (Typ. >30 dB)				>20 dB (Typ. >25 dB)
RF OUTPUT Transimedance Gain	10 x 10³ V/A^b		16 x 10³ V/A^c		28 x 10³ V/A^c
RF OUTPUT Conversion Gain	9 x 10³ V/W @ 1300 nm^b	7.2 x 10³ V/W @ 1060 nm^b	14.4 x 10³ V/W @ 1300 nm^c	11.5 x 10³ V/W @ 1060 nm^c	20 x 10³ V/W @ 1060 nm^c
RF OUTPUT Power at 1 dB Compression^c	-		+16.5 dBm Min +18 dBm Typ.
RF OUTPUT CW Saturation Power	420 µW @ 1300 nm	530 µW @ 1060 nm	See Note Below
RF OUTPUT Coupling	DC (AC Coupling Available upon Request)		AC Coupling Only
RF OUTPUT Impedance	50 Ω
Max Voltage Swing	±1.9 V for 50 Ω Load ±3.8 V for High-Impedance Load		See Note Below
Minimum NEP^d	8 pW/Hz^1/2 (DC to 100 MHz)		9.3 pW/Hz^1/2 (30 kHz to 100 MHz)	9.0 pW/Hz^1/2 (30 kHz to 100 MHz)	12.0 pW/Hz^1/2 (1 MHz to 100 MHz)
Overal Output Voltage Noise	<2.0 mV_RMS		<9 mV_RMS	<6.5 mV_RMS	<12 mV_RMS
MONITOR Outputs
MONITOR Output Impedance	200 Ω
MONITOR Output Bandwidth (3 dB)	DC - 3 MHz				DC - 2.5 MHz
MONITOR Output Conversion Gain, High Z Load^b	9 V/mW @ 1300 nm	7.2 V/mW @ 1060 nm	9 V/mW @ 1300 nm	7.2 V/mW @ 1060 nm
MONITOR Output Voltage Swing, High Z Load	10 V Max
Overall Output Voltage Noise	<0.65 mV_RMS
DC Offset	< ±2 mV
General
Electrical Outputs	SMA
Included DC Power Supply^e	±12 V @ 250 mA 100/120/230 VAC, 50 - 60 Hz, Switchable
Operating Temperature Range^f	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")
Weight	0.35 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.
For more information on NEP, please see Thorlabs' Noise Equivalent Power White Paper.
A replacement power supply that support input voltages of 100, 120, and 230 VAC 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:

Operation of Balanced Detectors with Bandwidths up to 400 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 400 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 V_p-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

Pin Diagrams for OCT Balanced Detectors

Monitor +/-

SMA Female

SMA Female

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

RF Output

SMA Female

SMA Female

For the PDB415, PDB425, PDB440, and PDB465 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 @ 1300 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)

PDB Female (Photodetector)

Pinout for PDA Power Connector

Posted Comments:

Markus Schmidt (posted 2021-06-19 23:06:57.393)

Hello I read PDB470C Manual. As I know for some Photodetectors, the bandwidth has relation with R_load. Is it right for PDB470C? for example if I add a 50 Ohm or 1 M Ohm R_load, what will be the photodetector bandwidth? Regards

soswald (posted 2021-06-28 08:51:07.0)

Dear Markus, thank you for your feedback. The bandwidth of the PDB470C does not vary with the terminating load. We recommend a 50 Ohm load for the RF output and Hi-Z for the Monitor outputs.

sebastian.marschall (posted 2013-09-23 13:17:20.217)

Hello What is the reason for the different frequency responses of the PDB480C-AC (1.6 GHz) and the PDB481C-AC (1.0 GHz). Would there be big problems when using the PDB480C-AC with 1060 nm light (coupling losses, mode-dispersion, etc.)? Regards, Sebastian

tschalk (posted 2013-09-26 06:29:00.0)

This is a response from Thomas at Thorlabs. Thank you very much for your inquiry. The bandwidth of the respective detector is defined by the pigtailed diodes built in. Those are designed for a specific wavelength, both because of the fiber used as pigtail as well as for the diode itself. The diode used in the PDB481-AC can unfortunately operate in a stable regime only up to 1GHz. While it would be in principle be possible to use the PDB480C-AC at 1060nm, the diode being not optimized for this wavelength would induce higher losses. The modal dispersion in this case should be negligible considering the short length of the pigtails. I will contact you directly with more detailed information.

OCT Balanced Detectors with Fast Monitor Output: 320 - 1000 nm

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Specifications^a
Item #	PDB440A	PDB425A	PDB415A	PDB465A
Wavelength Range	320 - 1000 nm
Detector Type	Si/Pin
Typical Max Responsivity	0.53 A/W			0.50 A/W
Active Detector Diameter	0.8 mm
Bandwidth (3 dB)	DC - 15 MHz	DC - 75 MHz	DC - 100 MHz	DC - 200 MHz
Common Mode Rejection Ratio	>35 dB		>25 dB
Transimpedance Gain^b	51 x 10³ V/A	250 x 10³ V/A	50 x 10³ V/A	30 x 10³ V/A
Optical Inputs	FC/PC or FC/APC (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 PDB4xxA Series Balanced Detectors

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OCT Balanced Detectors with Fast Monitor Output: 800 - 1700 nm

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Specifications^a
Item #	PDB440C	PDB425C	PDB415C	PDB465C
Wavelength Range	800 - 1700 nm
Detector Type	InGaAs/PIN
Typical Max Responsivity	1.0 A/W
Active Detector Diameter	0.3 mm			0.15 mm
Bandwidth (3 dB)	DC - 15 MHz	DC - 75 MHz	DC - 100 MHz	DC - 200 MHz
Common Mode Rejection Ratio	>35 dB		>25 dB
Transimpedance Gain^b	51 x 10³ V/A	250 x 10³ V/A	50 x 10³ V/A	30 x 10³ V/A
Optical Inputs	FC/PC or FC/APC (Removable)			FC/PC or FC/APC (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 PDB410C, PDB420C, PDB440C, and PDB460C Balanced Detectors

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OCT Balanced Detectors with Fast Monitor Output: Optimized for 1060 nm

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Specifications^a
Item #	PDB471C	PDB481C-AC	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)	DC - 400 MHz	30 kHz - 1.0 GHz	1 MHz - 2.5 GHz
Common Mode Rejection Ratio	>25 dB (Typ. >30 dB)		>20 dB (Typ. >25 dB)
Transimpedance Gain	10 x 10³ V/A^b	16 x 10³ V/A^c	28 x 10³ V/A^c
Optical Inputs	FC/APC
Monitor Output Bandwidth	DC - 3 MHz		DC - 2.5 MHz

For a full list of specifications, please see the Specs tab above.
Values for transimpedance 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.

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

Responsitivity of the Photodiodes in Detectors for 1060 nm

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The blue shaded region indicates the specified wavelength range for these balanced detectors. 1060 nm is marked with a vertical blue line.

OCT Balanced Detectors with Fast Monitor Output: Optimized for 1300 nm

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Specifications^a
Item #	PDB470C	PDB480C-AC
Operating Wavelength	Optimized for 1300 nm (1200 - 1700 nm Range)
Detector Type	InGaAs/PIN
Internal Coupling Fiber	SMF-28e+
Responsivity (Typical)	0.9 A/W @ 1300 nm
Active Detector Diameter	0.075 mm
Bandwidth (3 dB)	DC - 400 MHz	30 kHz - 1.6 GHz
Common Mode Rejection Ratio	>25 dB (Typ. >30 dB)
Transimpedance Gain	10 x 10³ V/A^b	16 x 10³ V/A^c
Optical Inputs	FC/APC
Monitor Output Bandwidth	DC - 3 MHz

For a full list of specifications, please see the Specs tab above.
Values for transimpedance 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.

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

Responsitivity of the PDB480C-AC Balanced Detector

Click to Enlarge
The blue shaded region indicates the specified wavelength range for these balanced detectors. 1300 nm is marked with a vertical blue line.

±12 VDC Regulated Linear Power Supply

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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.