S-42
The Tektronix S-42 is a sampling head for 1300 nm optical signals. It has an FC/PC fiberoptic connector for the input signal. It is essentially an S-4 sampling head with a photodiode at the input.
Specified accuracy is for connections through 8/125 μm single-mode fibre, although a lens in front of the photodiode allows connections using multi-mode fibre as well, at some degradation of response speed.
The manual shows it being used in a 7S12-driven TDR setup with an external OT503 electro-optic converter as the optical signal source.
Key Specifications
| Pulse response | 55 ps |
|---|---|
| Bandwidth | 6.4 GHz (equiv.) |
| Spectral response | 1000 – 1700 nm |
| Deflection | 50 μW/Div to 50 mW/Div @ 1300 nm |
| Noise equivalent power | 42 μWRMS max. |
| Max. nondestructive input | 10 mW mean, 125 mW peak |
| Features |
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Internals
The S-42 borrows heavily from the S-4 sampling head, re-using the S-4 strobe, sampler and preamp boards. It uses the same six-diode traveling-wave sampling gate, strobed by 125 ps pulses generated using a snap-off diode driven by an avalanche transistor.
The S-4's SMA input connector is still present internally, and driven electrically in some of the calibration procedures, with the photodiode removed.
To accommodate the photo diode, the S-42's case is longer than the S-4's. When inserted, the S-42 therefore protrudes from the base unit by about two centimeters.
Pictures
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block diagram
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schematic
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S-42 spectral response
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Description in 1989 Catalog
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