Generation of a 49-GHz, high-repetition-rate, all-polarization-maintaining, frequency-locked multicarrier
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摘要: 频域稳定的高重频多波长光源是信道化和光通讯等领域的理想光源。为了满足高重频多梳齿激光源的应用需求,本文研制了49 GHz梳齿间隔的多波长激光源。通过优化I/Q两端射频信号和三个偏置点,IQ调制器稳定工作在载波抑制单边带模式,杂散频率成分抑制比达到27.5 dB。本文利用循环调制技术产生宽带多波长光频梳,并通过优化射频功率建立环内增益-损耗平衡,有效提升平坦度,获得了梳齿间隔为24.5 GHz、梳齿数目为28根、平坦度仅为3 dB、梳齿信噪比(TNR)达29 dB的多波长光频梳。在此基础 上,进一步利用法布罗(FP)滤波技术将频率间隔提升到49 GHz,最终得到梳齿数目达14根,平坦度为2.7 dB,TNR达19 dB,平均光功率为9 dBm的高重频多波长光频梳。由于采用了全保偏光纤器件和集成化技术,本系统具有一键式启动和长时稳定运行的特点,运行半小时的功率抖动标准差仅为0.5%,有望在各微波光子领域中应用。Abstract: Frequency-locked multicarrier with high repetition rate is an ideal tool for microwave channelization and optical communications. To meet the needs of those applications, we propose a multicarrier laser with a repetition frequency of 49 GHz. The I/Q Modulator (IQM) works at the Single-Frequency Shifting (SSB) state by carefully optimizing the Radio Frequencies (RFs) and their three bias points, resulting in a signal-to-noise ratio of 27.5 dB. The Recirculating Frequency Shifter (RFS) architecture is employed to generate an optical comb with high flatness. By optimizing the power of RFs for the balance of gain and loss of intracavity, we successfully generate 28 frequency-locked subcarriers with flatnesses lower than 3 dB and Tone-to-Noise Ratios (TNR) larger than 29 dB. Meanwhile, an Fabry-Perot (FP) etalon is used to increase the repetition-rate, resulting in 14 frequency-locked subcarriers with flatnesses lower than 2.7 dB, TNR larger than 19 dB, average powers of more than 9 dBm and carrier spacings at 49 GHz. By applying all-polarization-maintaining components and integrated technology, the system shows one-push and long-term running properties. The standard deviation of power jitter of the multi-carrier frequency comb through the half hour is only 0.5%, which shows that this scheme has great potential applications in channel communications and microwave channelization.
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图 1 多波长光频梳系统装置图。CW:连续激光器,PM-OC:保偏分束器,FP:法布里-珀罗标准具,EDFA:掺铒光纤放大器,FBG:光纤光栅,BF:带通滤波,PD:光电探测器,EA:射频放大器,EC:射频功分器
Figure 1. Block diagram of multicarrier source system. CW: continuous wave laser; PM-OC: polarization-maintaining optical coupler; FP: Fabry-Perot etalon; EDFA: Erbium-doped fiber amplifier; FBG: fiber bragg grating; BP: band-pass filter; PD: photodiode detector; EA: electronic amplifier; EC: electronic coupler
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