High Optical Feedback Tolerance of a Detuned DBR Laser for 10-Gbps Isolator-Free Operation
Round 1
Reviewer 1 Report
The authors have studied the optical feedback tolerance (OFT) of a three-section distributed Bragg reflector (DBR) laser in both static and modulated states. The results confirmed the significant influence of wavelength detuning from the Bragg wavelength on OFT. When the DBR laser is working in the red-detuned region, the OFT can be greatly enhanced, which is favorable for both continuous and direct-modulation applications. The excess relative intensity noise (RIN) induced by optical feedback was remarkedly suppressed in the CW state under the feedback level of −9 dB. In the DM state, the red-detuned DBR laser also demonstrated superior stability against feedback.
I have the following comments regarding the paper:
1- The authors should explain the reasons for mode hoping. Also, discuss why the mode hopping points are randomly distributed for different lasers of the same batch, as mentioned in line 83 of Page-2.
2- The authors need to discuss why the feedback tolerance is high for the red detuned region compared to the blue region.
3- How did the authors measure the SNR from the eye diagram? The process should be explained. According to my understanding, optical spectrum is generally used for measuring SNR, not the eye diagrams.
4- What was the Bragg wavelength for the lasers used in the study? The authors have shown plots of lasing current versus wavelength, but it is not clear where the Bragg wavelength is on these plots.
5- Finally, I was not able to assess the novelty of this work. The authors have observed the response some DBR lasers in the presence of optical feedback. This behaviour of the lasers to feedback is well known, so what is new in this study?
6- Finally, there are some English mistakes, for example: "to prevent the impair from", "typical of which includes", etc.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The paper by Qiulu Yang investigated the static CW and dynamic DM performance of a 1.3 μm DBR laser under optical feedback. A considerable enhancement in optical feedback tolerance is obtained when the DBR laser is red-detuned from the Bragg wavelength. A BtB BER of 1×10-9 and 3×10-7 is obtained under a feedback level of -15 dB and -9 dB. After 20-km fiber trans-60 mission, the BER still maintains below 1×10−7 under a feedback level of −15 dB.
My overall opinion is that the paper can be accepted after minor revisions.
1. In line 67, the fabrication process should be described detailly.
2. The thickness of the gain section, phase section, DBR section and MQW structure is unknown and should be described.
3. In line 72, the room temperature is unclear.
4. In Figure 1c, there is only lasing wavelength for 55mA. The mode-hopping point at 53mA should be added.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
Tolerance of optical feedback of single wavelength lasers is a very important metric for optical communication applications. This manuscript did a systematic study of the influence of optical feedback on laser performance. I suggested publication after minor revision:
a. Shows spectra of laser under optical feedback (only laser peak wavelength in the current manuscript)
b. Simulation of tolerance to optical feedback by commercial software such as lumerical interconnect. (this can improve the quality but not necessary)
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The authors have addressed all my queries. I have not further questions regarding the manuscript.
