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.

Tektronix S-42
Optical Sampling Head
S42 Head

Compatible with 7000 and 3S series sampling heads

Produced from 1989 to 1990

Manuals
(All manuals in PDF format unless noted otherwise)

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
  • Mean power meter, dynamic range 5 nW to 5 mW (60 dB), bandwidth 100 Hz

Link

Documents Referencing S-42

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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