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O/E info:Responding characteristics
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Visible wavelength O/E
(Max NA = 0.2, 0.25) -
Visible wavelength O/E
(Max NA = 0.5) -
Visible wavelength O/E
(Hi-Sensitivity) - NIR wavelength O/E
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- O/E Selection Guide
- O/E Instruction
- O/E Dual-Balanced Detector
- O/E Dual-PD Amp for AFM
- JSTnews
- E/O LD Source
- E/O VCSEL Source
(670nm) - E/O VCSEL Source
(850nm) - 8xDFB-LD Laser
- HF level variable LD source
- Optical Coupler
- Optical Link System for Linac
- Optical Link for TTL
- Optical Link for NIM
- Optical link for analog Transceiver
(2KHz～3GHz) - TDM Opt-communication System(JAMSTEC)
- Waveform Analyzer DWA-xx
- Video line inserter
(for NTSC) - Bessel filter
* Responding characteristics of the PD in a range of convertible frequency bandwidth
Frequency characteristics of Si PD (Silicon Photodetector) is mostly affected by wavelength of the incident beam. The Figure 1 shows an example of frequency characteristics of a high speed Si PD.
The Si PD in the example of Figure 1 indicates a flat responding characteristics all the way up to greater than1GHz in case of incident beam of short wavelength 405nm shown in blue line. Meanwhile, in case of 850nm incident beam shown in magenta line, the response starts dropping gradually from 1.0 MHz. It remarkably appears when the wavelength of the incident beam becomes longer than the maximum sensitivity wavelength of the Si PD.
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Figure 1 |
The Si PD used in SPD-1, SPD-2, and SPA-2 show the same characteristics though, Graviton adjusts to make it flat as possible over the required frequency range, by applying different circuitry compensation constant against each reference wavelength. When these devices receive the incident beam which has different wavelength from reference wavelength, the frequency characteristics may not be kept in flat or may have distortions.
The figures below show the output voltage wave which is observed when shutting down the incoming beam to the O/E converter quickly.
Example of SPD-1_-650nm
The figure in your left is the case that incoming beam wavelength (658nm) is close to the reference wavelength (650nm). In such a case, the output voltage goes to the dark level, then becomes to a flat waveform. The figure in your right is the case that incoming beam wavelength (850nm) is longer than the reference wavelength (650nm). The circuitry compensation constant of the internal amplifier of SPD-1_650nm is not enough to adjust the incoming beam of 850nm. As a result, it shows the response in high frequency range goes down.
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Example of SPD-1_850
The figure in your left is the case that incoming beam wavelength (850nm) is close to the reference wavelength (850nm). In such a case, the output voltage goes to the dark level, then becomes to almost a flat waveform. The figure in your right is the case that incoming beam wavelength (658nm) is shorter than the reference wavelength (850nm). The circuitry compensation constant of the internal amplifier of SPD-1_850nm is too large to adjust the incoming beam of 850nm. As a result, it shows the response in high frequency range increases.
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There are some models of Si PD of which frequency characteristics are not affected by wavelength of the incident beam.
SPD-3, SPA-3, SPD-4 and SPA-4 employ such type of Si PD, the response against the frequency is not affected by the wavelength of incoming beam. In case you are going to apply for multiple wavelength using with a single E/O converter, one of those O/E converters is recommended.
Example of SPD-3
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| An output voltage waveform when the 658nm beam is inputted to SPD-3 and is intercepted rapidly. | An output voltage waveform when the 850nm beam is inputted to SPD-3 and is intercepted rapidly. |
