Femtosecond-Level Frequency Transfer at 10 GHz over Long Fiber Link with Optical–Electronic Joint Compensation

Round 1

Reviewer 1 Report

In this study, the authors demonstrated the transfer of a 10 GHz RF signal over 50-km long fiber using an optical-electronic phase compensator. The output of the results suggests that the optical-electronic phase compensator can be used as a replacement for the commercial H-master and Cs clocks.

Overall, the results are adequately presented and I recommend the publication of the paper after considering the following points.

-line 136-137: the DFB laser has a linewidth of 100 kHz, is this specified or measured?

- in section 3, the authors mentioned the manufactures of some of the components in their setup, but not for all the components, e.g., the servos, the DFB manufactures are not mentioned.

- shouldn't the details of the experimental setup, the manufactures of the used components, be mentioned in section 2?

- line 157 -158:  "Next, the principle of the optical active phase compensation will be explained in detail." What comes next is the principle of optical-electronic phase compensation and not the optical active phase compensation. This sentence should be changed to "Next, the principle of the optical-elecronic active phase compensation will be explained in detail."

- line 187, "In a normal day," What is a normal day? I suggest deleting it.

- lines 206: "shown in Fig. 3" should be Fig. 4, right?

- line 206: "short link": How short was it?

-line 207: "Curve(iii)" should be "Curve(c)"

 

- In the discussion section, I missed a detailed comparison with what is previously done by other authors. A table summarizing what people did before will be helpful and increases the impact of the manuscript.

-line 241: "can achieve low-noise frequency transfer": How low? as I said a comparison with what people did would be really helpful.

 -Minor English revision is still needed:  "On transmitter" , and "on receiver" may be written differently, e.g., "on the transmitter side.

The use of the definite article "the" may be used in several parts of the manuscript.

 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

The paper entitled “Femtosecond-level frequency transfer at X-band over long fiber link with joint optical-electronic compensation” presents a fiber-based RF transfer method with OE compensation with high stability. Please refer the comments below.

1.     Please provide a table to compare previous research of RF transfer approaches with key parameters.

2.     The author claims that this work can be applied to X band. however, Both EO and OE conversion is frequency dependent. It is not convincing to claim this method is universal at X band with only single frequency (i.e. 10 GHz) experiment. The bandwidth and precision of phase compensation is also highly related to the working frequency.

3.     What is link budget of such a microwave photonic system? If the system consumes a large power to achieve the RF transfer stability, is this improvement significant? Please provide the metrics and discussion about this trade-off.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf