Ripple Suppression in Broadband Microwave Photonic Phase Shifter Frequency Response
, Bijuan Chen 1, Erwin H. W. Chan 2, Xudong Wang 1,*, Xinhuan Feng 1 and Bai-Ou Guan 1
Round 1
Reviewer 1 Report
Broadband microwave phase shifters are important components in many microwave photonic systems. The paper studied the performance of commercial phase shifters in terms of the ripples in their frequency responses (both amplitude and phase) and proposed a microwave photonic solution to reduce those ripples. The experimental results are technically sound. Therefore, the paper can be considered for publication after the following issues have been addressed.
(1) Three commercial RF phase shifters have been tested with the results shown in Fig. 1. Are the three phase shifters the same model? What are their specified operation bandwidth?
(2) Fig. 1 only shows the response of 90-degree hybrid couplers. What other factors can contribute to the response ripples of a microwave photonic phase shifter based on OPS+OFS structure. It is better to show the measured over all MWP phase shifter response as well.
(3) Equation (3) is not properly displayed in the pdf version I have.
(4) The main finding from eqs (5)-(8) is the MPPS output is depend on the amplitude and phase of the two RF signals into the DPMZM. It is not clear how it is related to the response ripples of the 90-degree hybrid coupler.
(5) Since the OPS is embedded in the Dual-polarization DPMZM, a detailed internal structure of the dual-polarization DPMZM could be shown in Fig. 4.
(6) At the end of section 2, it was concluded that a low noise figure optical amplifier is required. However, in the experimental demonstration only an optical filter was used. What is the insertion loss of this optical filter and do you need an optical amplifier to further improve the phase shifting performance?
Author Response
Please see the attachment
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The paper by Weicheng et al. proposed a solution to reduce the ripples in the frequency response of a microwave photonic phase shifter (MPPS) implemented using a 90 hybrid coupler. But there are too many issues. I can’t recommend the acceptance of it till my concerns below are addressed:
-Motivation is not clear. The use of hybrid coupler has already been used in MPPS before. So what is the main contribution/difference compared with the previous report? Any special consideration for your work? Especially, what is the advantages of your solution compared with others?
-In theory part, how are equations deduced? Please give suitable references used. Some part in Eq. (3) can’t be seen.
-What is ‘MPPF’?
- What is RBW used for OSA?
-The logic is a bit messed and some part is hardly to follow. Please sort it.
-The English is Chinglish and very casual at many places (such as ‘Title’ in your title, ‘ response results from the.’,’ the turn period’, ‘by a pair of 90 phase difference RF signals from a ’, ‘VPItransmissionMarker photonic simulation software.’, ‘compared to a fiber’, ‘compensate for the insertion loss of’, ‘single compact modulator bias controller ’, ‘with (red dotted line) and without (blue solid line) including the optical’,’ with the inclusion’, etc.). The author should get some English expert to polish the language issues carefully and thoroughly.
-Please check the use of the article word of ‘the’.
-In conclusion part, what is ‘for the first time’ to emphasize? Is it suitable?
- Some reference format/style is a bit messed (like 1, 4, 8). This should be revised and unified.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
All my concerns have well been responded and I recommended the acceptance for the publication.
