Photonic Microwave Distance Interferometry Using a Mode-Locked Laser with Systematic Error Correction

Round 1

Reviewer 1 Report

The paper presents the method of correction systematic error, passive and active, of photonic microwave distance interferometer. The measurement position and proposed method evaluation of metrological properties of this device are presented. The results are interesting from theoretical and practical point of view.

The paper has good scientific level and is written in good language, but some of the sentences are too long. Therefore some parts of this paper are difficult to understand. I recommend to take this fact into account in future publications.

The list of References is sufficient.

Below,  a few remarks were presented. Please take them into consideration in final version of this article.

 

 

1. The description on Figure 1a, L and Q, is too unreadable, I recommend to change them.
2. In Figure 3d, the green line present no optical power but amplitude of photodetector output signal in mV.
3. The equation on line 142 hasn’t number. Please complete the number.
4. Please complete the phrase in line 171 “Figure 5 show or present the result …”

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors demonstrate measurement of meter-size distances with accuracy on the order of micrometers. This is performed by using femtosecond laser delivering pulses with stable repetition rate of 100 MHz. The beam is divided into the probe and reference beams. Both of them are detected and converted into the electrical signals, then mixed with the local microwave oscillator signal and further phase-analysed. It is shown that the measurement accuracy can be substantially improved by compensating the systematic error caused by the laser pulse energy fluctuations that affect the phase of the received signals. The paper looks as a solid and complete piece of work that could be of interest for the readers of the journal. I suggest only minor revisions that could help a broader audience of the readers to understand the work.

1) Since the work deals with the ultra-short laser pulses, some illustrations of the measurement principle in time-domain could be useful in addition to the frequency-domain considerations provided in the paper.

2) The blue and green beams are not shown in Fig. 1 as it is mentioned in the text. 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf