Wuhan Research Institute Of Mpt

Wuhan, China

Wuhan Research Institute Of Mpt

Wuhan, China
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Yuan Y.,Huazhong University of Science and Technology | Li W.,Huazhong University of Science and Technology | Han J.,Huazhong University of Science and Technology | Feng Q.,Huazhong University of Science and Technology | And 4 more authors.
Chinese Optics Letters | Year: 2017

A dual optical time domain reflectometry (OTDR) system, which employs two different continuous waves at the optical line terminal and a pair of fiber Bragg gratings at the end of each optical network unit, is proposed in a time-division multiplexing passive optical network (PON). The proposed scheme accomplishes the fiber fault monitoring by comparing the different wavelength's testing curves. Complete complementary code is utilized to measure multiple wavelength signals simultaneously with only one receiver and to improve the dynamic range of this system. The PON system consisting of 20 km feeding fiber and a 1:16 splitter is investigated by the experiments. The experimental results show that the faulty branch can be successfully identified by using our scheme. What is more, we also demonstrate that our scheme can be applied to the multi-stage PON. © 2017 Chinese Optics Letters.


Han J.,Huazhong University of Science and Technology | Li W.,Huazhong University of Science and Technology | Huang L.,Accelink Technologies Co | Li H.,Accelink Technologies Co | And 2 more authors.
IEEE Photonics Technology Letters | Year: 2016

A low complexity carrier phase estimation (CPE) for 16-QAM systems is investigated in this letter. First, we propose a single-stage CPE algorithm based on the error function calculation. In this CPE algorithm, we define an error function and use the four error function values corresponding to four test phase angles (-π/4, -π/8, 0, and π/8) to directly calculate the optimal phase angle, which effectively reduces the computational complexity compared with the blind phase search algorithm. Next, we combine the proposed CPE algorithm with an improved V&V algorithm and propose a two-stage CPE algorithm, which has both advantages of good linewidth tolerance and low computational complexity. Through simulations, the effectiveness of the proposed algorithms is demonstrated in a 28-Gbaud 16-QAM coherent optical transmission system. © 1989-2012 IEEE.


Feng Q.,Huazhong University of Science and Technology | Li W.,Huazhong University of Science and Technology | Zheng Q.,Huazhong University of Science and Technology | Wang J.,Huazhong University of Science and Technology | And 3 more authors.
IEEE Photonics Journal | Year: 2017

In this paper, first, we employed the coupled-mode theory to investigate the backscattering power characteristics of Rayleigh backscattering (RB) and stimulated Brillouin scattering (SBS) both synchronously and precisely. We discovered how the RB and SBS power changed with pump powers and fiber lengths. The scattering power curves with different pump powers could be divided into three regions. The first was called 'the linear region of RB,' in which the pump power was mainly converted into RB and the RB power grew linearly with pump powers. The second region was called 'the stimulation region of Brillouin scattering,' in which the power was mainly converted into SBS. In 'the gain-saturated region,' when the pump power was much higher than the SBS threshold, both the RB and SBS power were gain-saturated. We also obtained the power curves with different fiber lengths. The power curves were helpful to set up proper launch powers in practical engineering applications, such as optical time-dome reflectometry systems and distributed fiber sensors. Then, we verified our theoretical results by experiments. Finally, according to the measurements and numerical solutions of the coupled-mode equations, we discussed the application of backscattering and gave advice for pump power selections in different fiber link monitoring systems. © 2009-2012 IEEE.


Li Y.,Central China Normal University | Wang Y.,Huazhong University of Science and Technology | Li W.,Huazhong University of Science and Technology | Han J.,Huazhong University of Science and Technology | And 4 more authors.
Photonic Network Communications | Year: 2015

A novel uplink data transmission method in electrical code division multiplexing passive optical networks is proposed, simulated and experimentally verified, in which each optical network unit (ONU) is assigned a special multi-level orthogonal code based on wavelet packet transform. Comparing with the normal bi-level orthogonal code by using Walsh code or Gold code, the proposed method can improve the bandwidth utilizations and reduce the optical beat noise. Simulation results show 31 ONUs, of which each data rate is 10 Gb/s and total rate is 310 Gb/s, can be transmitted 30 km. Three ONUs with each data at 622 Mb/s over 50-km single-mode fiber is experimentally demonstrated. © 2014, Springer Science+Business Media New York.


Feng Q.,Huazhong University of Science and Technology | Li W.,Huazhong University of Science and Technology | Zheng Q.,Huazhong University of Science and Technology | Han J.,Huazhong University of Science and Technology | And 6 more authors.
Optics Express | Year: 2015

The backscattering noises introduced by Rayleigh and stimulated Brillouin scattering have been experimentally studied by means of their spectrum broadening, the scattering power variation and their impacts on upstream signals with different transmission fiber lengths and incident powers in a single-fiber bidirectional passive optical network (PON) communication system. The results show that both spontaneous scattering and simulated scattering can take place. The power and spectrum of backscattering noises are determined by the downstream launch power, laser linewidth and transmission fiber length. With the transmission length increasing, the power of backscattering noises gets higher, the spectrum of the backscattering noise broadens and the simulated threshold power decreases. The backscattering noise can beat with uplink light to modulate envelop of upstream signal resulting in degradation of BER greatly. Under the condition of one single channel for the second next generation PON (NG-PON2), the fiber length is 40km and downstream launch power is up to 11dBm. At this time, the backscattering noises are easy to be stimulated and the scattering power rises up from -20dBm to 10dBm, which can overwhelm the US signal. The spectrum of the optical beat interference noise also rises up with fiber length, which causes the uplink's BER degradation. The experimental results are significant for mitigation of backscattering noises under the condition of bidirectional PONs. © 2015 Optical Society of America.

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