Compact Four-Channel Optical Emission Module with High Gain

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have presented comprehensive design and test of a compact four-channel optical emission module. In general, this manuscript is well written and easy to follow. I have two questions about this work before it can be accepted for publication in Photonics.

(1) In the measurement of S21 curve, the parameters of the photodetector (PD) should be given. Especially, the noise figure is a parameter related to the radio-over-fiber (RoF) link, instead of the optical emission module itself. Therefore, the authors should clarify this issue in the manuscript to avoid confusion.

(2) The authors state that the module can operate at stable temperatures across an ambient range of -55°C to 75° However, this conclusion is only supported by simulation. The authors should provide test data to support this conclusion.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This manuscript presents a four-channel high-gain optical emission module with a compact structure integrating DML chips, LNA chips, and control circuits. The current version needs to be minor revised before acceptance. My concerns are listed as follows.

1. The authors mention that the optical emission modules in Ref. [19] has a smaller size. The author should further clarify the distinctions between this work and Ref. [19] to better highlight the innovation of the proposed method.

2. The author mentioned that "the module has the ability to operate at stable temperatures across an ambient range of -55°C to 75°C," "Based on the microchannel liquid cooling solution, the module's thermal performance was simulated across a wide temperature range of -55°C to 75°C," and " employing water as the coolant." Given that water is used as the coolant, how is the microchannel structure protected from damage at -55°C? The author should give an explanation. Additionally, The author should elaborate on the practical implementation of the microchannel liquid cooling system. How is it connected externally? Does it require an external liquid pump?

3. In Section 3.4 (Simulation), the double lenses coupling scheme’s alignment tolerances in the X, Y, and Z directions were simulated. The corresponding experimental results for coupling tolerance tests should be added to validate the simulation.

4. Test results of S21 and the measured and simulated gains of the optical emission module with or without LNA as shown in Figure 19. Notably, the measured gain of the LNA deviates significantly from the simulation, the simulation shows a downward trend, while the measured result first rises and then declines. This discrepancy has also been affect the integrated optical transmitter module’s performance. Please analyze the reasons for the inconsistency between the measured and simulated values, and the measurement results showing first increase followed by a decrease should also be explained.

5. The noise figure of the optical transmitter module was tested. However, when the system’s noise figure approaches approximately 30 dB, instrument measurement errors become relatively large. The authors should supplement the description of the test system and methodology in the paper to ensure reliability.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Dear colleagues!
I think that your article is a good example of current and necessary in today's practice of microwave photonics development for wide-range telecommunication and sensor network applications. Judging by its content, the article touches a wide spectrum of model and physical experiments, a multi-sided study of technological aspects of the development, its comparison with similar developments, supported in the introduction by the presentation of various analogues. It is obvious that a four-channel solution can be obtained by simply addition of four laser sources. However, the compact solution you present allows to obtain a universal solution, both in terms of demand and in terms of simplicity of control, and especially in terms of internal monitoring, which is known to be a critical requirement for any microwave photonics systems, for example, when the external operating conditions change. Summary, I recommend your article for publication as is.

Author Response

Thank you sincerely for your thorough evaluation of our work. Your expert perspective reinforces the practical significance of this research, and we are encouraged to further advance this field.

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The author has replied to all the questions.