Terahertz oscilloscope (theoretical) - Page 1
Forum section: electronics / testgear

author: FrankenPC
author_rank: Unknown
timestamp: March 05, 2015, 05:33:25 pm
content: It's not much to look at now, but it may be the beginning of a whole new branch of oscilloscope technology some day.http://arstechnica.com/science/2015/03/research-confirms-that-lasers-improve-everything-including-oscilloscopes/An oscilloscope is designed to display changes in voltage or current with respect to time. To do this, the oscilloscope needs to sample the voltage faster than it changes, which is problematic for today's modern, high-frequency electronics, where it's often easier to generate fast changes than it is to measure them.This is where a laser may have some benefit. In principle, a light field can be modulated at a rate that is a large fraction of its base frequency (~600THz). Provided we can measure that modulation, we can measure time-varying voltages much faster than we could using any electronic method. But therein lies a conundrum: how do we measure the modulation of a light field? Using electrons. And what is the problem with electrons? They are too damn slow.

author: dom0
author_rank: Super Contributor
timestamp: March 05, 2015, 06:31:07 pm
content: I thought the new LeCroy scopes with xxx GHz bandwidth already use some kind of opto-electrical-mumbojumbo-conversion?

author: quarros
author_rank: Regular Contributor
timestamp: March 05, 2015, 06:34:19 pm
content: Quote from: FrankenPC on March 05, 2015, 05:33:25 pmThis quote from the article... I dont get it.I understand the advantages of using light as a measuring tool for smaller (from the time domain perspective) measurements. But ultimately the data is going to be collected by an electronic A/D converter, (which you can parallel for greater performance), but that is still using electricity to capture the data and it is not so different from our current approach with oscilloscopes. So can anyone shed more light on the subject? What I'm missing?Here is a link for the original paper:http://www.opticsinfobase.org/ol/abstract.cfm?uri=ol-40-2-260

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: March 05, 2015, 06:49:40 pm
content: Like this?http://w140.com/tekwiki/wiki/7J20

author: dom0
author_rank: Super Contributor
timestamp: March 05, 2015, 06:54:29 pm
content: No, that's just an optical spectrum analyzer (OSA).

author: electr_peter
author_rank: Unknown
timestamp: March 05, 2015, 06:54:37 pm
content: It is an equivalent sampling scope with very narrow BW.Laser pulses are correlated with the event they measure - laser pulses are of e-15s order, pause between pulses is of e-9s order. Phase of the laser is modified with mirror system. Actual voltage correlates with emitted electron energy. They do this many times and get a picture.Definitely useful for some things, but it is not exactly a true scope. It is a sampling device for a repeating signal.

author: dom0
author_rank: Super Contributor
timestamp: March 05, 2015, 06:55:53 pm
content: So the optical system is "just" used to essentially implement a very fast, low jitter aperture (sampling switch)?

author: JackP
author_rank: Regular Contributor
timestamp: March 05, 2015, 07:00:23 pm
content: About the 100GHz scope watch the signal path video on it. It shows how they get the bandwidth, something about splitting the signal into components ie 0-33GHz, 34-66GHz and 67-100GHz.Jack

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: March 05, 2015, 07:06:34 pm
content: Quote from: FrankenPC on March 05, 2015, 05:33:25 pmThat's almost verbatim from the 1960s Tektronix sampling scope manual...