Power-over-Fiber with Simultaneous Transmission of Optical Carrier for a High Frequency Analog Signal over Standard Single-Mode Fiber

Round 1

Reviewer 1 Report

Efficient simultaneous transmission of light and an optical carrier for transmitting a high-frequency analog signal was showed.  However, authors need to describe motivation of the research, previous publication information, and summary of the measurement need to be further described in the revision. In addition, English grammar and styles need to be improved so please ask professional English service or ask native English colleague. There are some comments as below.

1. Acknowledgments section need to be deleted if there is nothing.

2. In conclusion section, authors need to provide motivation of the research and future work.

3. Please provide the summary of the results with previous scholar's work for further comparison.

4. Authors must show in detail analysis of the previous research in the introduction section such as advantages and disadvantages.

5. Figures 2 and 4 label size is small.

6. In abstract, authors need to show motivation of the research in detail. 

7. Authors showed schematic of proposed system. But there is no Figure of real system ?

8. Please use abbreviated journal name in the reference section.

Author Response

First of all, we would like to express our sincere gratitude to the Reviewer for your attention to our manuscript and valuable criticisms that, no doubt, will contribute to a better presentation of our study. 

Efficient simultaneous transmission of light and an optical carrier for transmitting a high-frequency analog signal was showed.  However, authors need to describe motivation of the research, previous publication information, and summary of the measurement need to be further described in the revision.  

We have rewritten the introduction slightly to emphasize motivation. Fourteen references are given to previous work in the field of simultaneous power and signal transmission. 

In addition, English grammar and styles need to be improved so please ask professional English service or ask native English colleague.  

We really are very sorry. English is not our native language. We have revised the English by employing the services of a professional translator. Hopefully the English will get better, despite a rather short term for that manuscript revision (within a 5-day period). 

There are some comments as below. 

1. Acknowledgments section need to be deleted if there is nothing.
   
   The Acknowledgments section removed.
    
2.  In conclusion section, authors need to provide motivation of the research and future work. 
   
   “The use of transmitted power for signal amplification and improvement of RoF performance is the subject of future research and system optimization” was added to the Conclusion section to outline the direction of possible future work. 
   
   
3.  Please provide the summary of the results with previous scholar's work for further comparison. 
   
   A comparison of the obtained results with the results of previous work on the simultaneous transmission of optical power and optical information signal has been added to the Conclusion section. “These results are comparable to previous results of simultaneous transmission of 1064.8 nm high-power light and 1550 nm 5G NR 64QAMOFDM optical signal over 1 km single-mode fiber [14]. Note that for a given power delivery distance, there is an optimum wavelength with maximum transmission efficiency, which is a compromise between optical fiber loss, with a minimum at 1550 nm, and photovoltaic converter efficiency, which is inversely proportional to wavelength. The addition advantage of the wavelength (976 nm) is the availability of standard commercially available fiber optic components, laser diodes for EDFA pumping, and a cheaper and more reliable silicon-based photovoltaic converter, making our approach very cost-effective. The maxi-mum transmitted optical power may be increased in the future by wavelength multiplexing.”
   
   
4.  Authors must show in detail analysis of the previous research in the introduction section such as advantages and disadvantages. 
   
   Fourteen references are given to previous work in the field of simultaneous power and signal transmission in the Introduction section. A particular attention was paid to systems based on single-mode fiber Ref. 13 and 14. “Recently, optically powered RoF transmitting systems using a single mode fiber (SMF) have been demonstrated [7, 13, 14], which is of particular interest because the SMF is widely deploying in optical networks. Different wavelengths were used for the power transmission. The shorter wavelength of 830 nm [13] provides higher photovoltaic conversion efficiency, which is inversely proportional to the wavelength, while the longer wavelength of 1064.8 nm [14] has lower losses in the optical fiber. The error-vector magnitude is usually used to describe an influence of high power light on optically carried information signals. This is a complex digital signal transmission characteristic that generally depends on the modulation format. Thus, more general criteria independent of the modulation format are needed to evaluate optically powered RoF transmission systems.” The expected benefits of our system were also mentioned. “The wavelength of 976 nm provides lower optical losses than 830 nm and can be converted by a cheaper and more reliable silicon photovoltaic converter, in contrast to the A3B5 based converter used in previous works. A commercially available 976 nm high power laser pump diode for erbium doped fiber amplifiers was used. The primary analog signal transmission characteristics (gain, noise figure, and spurious-free dynamic range SFDR), independent of modulation formats, were used to determine the effect of strong light on the RF signal.”
   
   
5.  Figures 2 and 4 label size is small. 
   
   Font size increased in Fig.2 and Fig.4 
   
6.  In abstract, authors need to show motivation of the research in detail.  
   
   The motivation for the study is given in the Introduction section. Only brief results are presented in the abstract due to space constraints. 
   
7.  Authors showed schematic of proposed system. But there is no Figure of real system ? 
   
   The photo of the setup parts were added to the Fig. 1  
   
   
8.  Please use abbreviated journal name in the reference section. 
   
   Abbreviated journal titles such as J. Lightwave Technol., IEEE Commun. Mag. and etc. have been used in the Reference section.

Reviewer 2 Report

This piece of work is of interest to the community. However, one important aspect should be addressed before application, i.e., it is stated that the SFDR is close to the shot noise limit, more evidence or reasoning should be given to solidify the statement.

Other minor issues: In figure 2b, the plot has double vertical axes, it should be clearly noted that which curve corresponds to which vertical axis. Caption of Figure 4a is also erroneous.

Author Response

First of all, we would like to express our sincere gratitude to the Reviewer for your attention to our manuscript. Comments of the Reviewer were highly insightful and enabled us to greatly improve the quality of our manuscript.

This piece of work is of interest to the community. However, one important aspect should be addressed before application, i.e., it is stated that the SFDR is close to the shot noise limit, more evidence or reasoning should be given to solidify the statement. 

A theoretical estimate of the noise figure in the shot noise approximation has been added to the High frequency analog signal transmission performance section. 

Other minor issues: In figure 2b, the plot has double vertical axes, it should be clearly noted that which curve corresponds to which vertical axis. Caption of Figure 4a is also erroneous. 

The arrows have been added to the plots in Fig. 2b to show their relationship to the vertical axes.

Caption of Fig. 4 has been corrected: “(a) The optical noise power density versus radio frequency: (1) – 976 nm LD is switched off, (1) – 976 nm LD is switched on. (b) Noise figure as a function of signal frequency (1) is the standard mode of amplitude modulation with direct detection; (2) is the balanced mode.”