Dear Respected Mentors,Researchers and Colleagues
With reference to the paper attached herewith,Please make clear the highlighted text in yellow color.
We generate the UWB mono-cycle or doublet pulses all-optically by using electrical RF/base band data in the form of Gaussian Pulses to modulate the pulsed lasers.In this paper attached,what will be the electrical UWB signal which is modulating the light source??Is it simply e.g 5Gb/s RF/base band signal in the form of "0" and "1" generated by a PRBS generator or some other form of data????Please explain as i will be highly obliged
Regards
I had to read and re-read that paper, to understand what they are doing. Best I can tell, there is an electrical baseband signal which is mixed with an electrical UWB signal. The baseband signal might be a sequence of 0 and 1 bits, and must be within a spectrum of 0 - 3.1 GHz. When mixed with the much higher frequency electrical UWB signal, this will create a train of UWB chips, essentially, transmitted in the spectrum 3.1 - 10.6 GHz. I'm going by the description in Section 2.
These UWB "chips" would be little blips of energy, in the time domain, with some property like low to high or high to low amplitude, over a specified extremely short time interval, to indicate a + or a -. Each baseband data bit is represented by a sequence of these chips. Some predetermined sequence of + and - chips is used to represent a 1 data bit, and a different sequence of chips is used to represent a 0 data bit. This is basically direct sequence UWB, much like direct sequence CDMA. (A correlation receiver would then be used, to sync up with the string of chips at the receive end. But let's not get ahead of ourselves.)
So, it is this train of chips that is used to modulate a laser, in the MZM, and that light is sent through a single mode fiber.
The part you highlighted describes their test setup. But it looks like they either deviate from what they described in Section 2 somewhat, when describing the spectrum used by the wired UWB signal, or there's a small but confusing typographical error.
The wired UWB signal should be in the range 3.1 to 10.6 GHz, yet they claim 1 GHz. I have to believe that the 1 GHz reference is what they previously called "electrical signal," meaning the baseband bitstream, in the 0 to 3.1 GHz spectrum, and NOT the wired or electrical UWB signal as they claim. Very confusing terminology. Anyway, they receive that signal down a 36 km fiber, and then send it back upstream, and demodulate, to test out their concept.
UWB signal in electrical domain is a unique signal having ps pulse width and specialized form such as "UWB mono-cycle pulse" or "UWB Doublet pulse".UWB mono or doublet pulses can be obtained by getting 1st or 2nd order differential of gaussain pulse.
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