【摘要】：光載無線傳輸(ROF)將無線通信技術(shù)和有線的光網(wǎng)絡(luò)技術(shù)結(jié)合,利用光纖的大帶寬、低損耗的特點(diǎn),在長距離傳輸中具有很多優(yōu)勢。然而,ROF傳輸系統(tǒng)中激光器相對強(qiáng)度噪聲是制約系統(tǒng)性能的重要因素之一。在數(shù)字相干光通信中,平衡探測是降低相對強(qiáng)度噪聲的有效手段,對ROF模擬光通信系統(tǒng)具有重要的借鑒意義。本文對ROF傳輸系統(tǒng)中采用平衡探測降低相對強(qiáng)度噪聲的可行性及其影響因素進(jìn)行了研究,研究內(nèi)容如下:1.對ROF系統(tǒng)中平衡探測降低相對強(qiáng)度噪聲的方法進(jìn)行了理論分析。證明了可以通過消減直流電流項降低相對強(qiáng)度噪聲,但是引入的相位差噪聲、本振光強(qiáng)度和相對強(qiáng)度噪聲會影響降低的效果。在此基礎(chǔ)上在VPI平臺上建立了平衡探測模型,并進(jìn)行了仿真驗證,仿真表明ROF鏈路中平衡探測相比于直接探測降低了相對強(qiáng)度噪聲8.6dB/Hz。2.研究了信號光和本振光的功率值,信號光激光器和本振激光器的RIN值,以及信號光激光器和本振激光器線寬值對相對強(qiáng)度噪聲降低的影響。VPI仿真驗證表明隨本振光與信號光功率增加,信號光激光器的RIN值增加和本振光激光器RIN值的降低,系統(tǒng)RIN值會降低。信號光和本振光激光器的線寬值的增加會劣化相對強(qiáng)度噪聲的降低效果,但其主要受限于線寬較大的一只激光器。根據(jù)這些特性進(jìn)一步進(jìn)行了檢測信號的仿真分析,對比星座圖和計算所得RIN值發(fā)現(xiàn)平衡探測系統(tǒng)性能得到了提升。3.對平衡探測中雙路失衡的影響進(jìn)行了研究。對三種失衡因素(傳輸延時、耦合器分光比和探測器響應(yīng)度)對降低RIN的影響分別進(jìn)行了理論分析和仿真驗證,結(jié)果表明在相對傳輸延時越小,耦合器分光越均勻,探測器的響應(yīng)度越接近一致時,平衡探測相比于直接探測能夠更有效的降低相對強(qiáng)度噪聲,其中傳輸延時對相對強(qiáng)度噪聲的影響具有周期性。當(dāng)超過一定失衡范圍時,平衡探測不能降低相對強(qiáng)度噪聲。結(jié)合激光器線寬的影響,對雙路失衡的容忍范圍進(jìn)行進(jìn)一步研究,對平衡探測所能容忍的最大延時范圍以及探測器響應(yīng)度之比和耦合系數(shù)進(jìn)行了仿真分析。仿真結(jié)果表明隨著激光器線寬的增加,平衡探測雙路所容忍的失衡范圍會明顯減小。
[Abstract]:Optical borne wireless transmission (ROF) combines wireless communication technology with wired optical network technology, and makes use of the characteristics of large bandwidth and low loss of optical fiber, which has many advantages in long distance transmission. However, the relative intensity noise of laser in ROF transmission system is one of the important factors that restrict the performance of the system. In digital coherent optical communication, balance detection is an effective means to reduce relative intensity noise, which is of great significance for ROF analog optical communication system. In this paper, the feasibility and influencing factors of using balance detection to reduce relative intensity noise in ROF transmission system are studied. The method of reducing relative intensity noise by balance detection in ROF system is analyzed theoretically. It is proved that the relative intensity noise can be reduced by reducing the DC current term, but the effect of the reduction will be affected by the phase difference noise, the local oscillator intensity and the relative intensity noise. On this basis, a balance detection model is established on VPI platform, and the simulation results show that the balance detection in ROF link reduces the relative intensity noise by 8.6 dB 鈮，

本文編號：2487505