19.25Gb/s双频无色OOFDM在25km SSMF IMDD系统中的创纪录实测

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该研究论文展示了在25公里标准单模光纤(SSMF)上的创新成果，实现了19.25吉比特每秒(GB/s)的实时端到端双频光正交频分复用(OFDM)无色传输，这是前所未有的高数据速率。这一突破是通过利用反射电吸收调制器(REAM)结合强度调制和直接检测技术来完成的。实验中，系统采用了两个独立的调制方式：基带OFDM（0-2 GHz）和通带OFDM（6.125 ± 2 GHz），分别支持9.75 GB/s和9.5 GB/s的数据速率。这些子带信号由FPGA（现场可编程门阵列）驱动的数字信号处理(DSP)时钟同步，即使在低至100 MHz的工作频率下，以及DAC（数字模拟转换器）和ADC（模拟数字转换器）采样速度仅为4 GS/s的情况下，也能够保证高效传输。通过8 GHz的REAM，两个子带信号被电复用到单个光载波上进行强度调制。实验的关键在于对REAM的无色特性进行深入表征，以找到最佳的操作条件，从而优化整个OOFDM收发器和系统的性能。实验结果表明，在C波段的不同波长下，尽管最小接收光功率在0.5 dB的范围内有所变化，但基带和通带信号的误码率性能基本保持一致。这证实了系统的鲁棒性和稳定性。此外，研究人员还详细研究了最大信号线速率对RF子带功率变化的敏感性，发现系统在面对功率波动时，其性能表现具有一定的抗扰性。这项研究不仅提升了光通信系统的数据传输能力，而且为未来更高速率、更远距离的无色光通信系统提供了新的设计思路和技术参考。这篇论文不仅记录了一项重要的技术里程碑，也为电光调制器在长距离、高速率光通信中的应用开辟了新的可能性，对于推动光通信技术的发展具有重要意义。

flexibility and wavelength scalability, virtual point-to-point connection enabling each

individual end-user to be granted a single wavelength, protocol transparency and excellent

network security [1,2]. To practically deploy WDM-PONs, the main challenges are cost-

effectiveness and colorlessness of optical network units (ONUs). To address such challenges,

several techniques have been proposed, which include, for example, spectrum-slicing of super

luminescent diodes (SLDs) or optical amplifiers [3,4], wavelength tunable lasers in ONUs

[5,6] and remote modulation of reflective intensity modulators [7,8].

Among all the aforementioned techniques proposed previously, reflective intensity

modulator-based ONUs are very attractive for WDM-PONs since the implementation of

centrally-controlled dynamic wavelength management in an optical line terminal (OLT)

allows the reflected upstream signal transmission from the ONU in a wavelength agnostic

manner. More importantly, since ONU-side laser sources are not present, the ONU

transceiver complexity is greatly simplified and consequently the overall WDM-PON

installation cost is significantly reduced by a factor proportional to the total number ONUs

accommodated simultaneously in the network. To achieve reflective intensity modulation-

based cost-effective ONUs, reflective intensity modulators that can be utilized include, for

example, reflective semiconductor optical amplifiers (RSOAs) [9–11], reflective electro-

absorption modulators (REAMs) [12–14] and reflective Fabry-Perot lasers [15–17]. Among

these reflective intensity modulator candidates, REAMs can be easily scaled for data line

rates higher than 10Gbits/s compared to other reflective modulators due to their high

modulation bandwidths. For example, 40Gb/s transmission over 20km standard single mode

fiber (SSMF) with offline digital signal processing (DSP) has been achieved by using a

20GHz SOA-REAM.

To further enhance the performance and flexibility of WDM-PONs and still maintain their

compatibility with existing time-division-multiplexed (TDM) PONs, optical orthogonal

frequency division multiplexing (OOFDM) has been considered as one of the strongest

contenders for practical applications [18], since OOFDM has inherent and unique advantages

including adaptive provision of hybrid dynamic bandwidth allocation (DBA) in both the

frequency and time domains, significant reduction in network complexity, adaptability to

imperfect transmission system characteristics and potential for cost-effective mass

deployment. It is, therefore, preferable if use is made of OOFDM signals in REAM-based

ONUs in WDM-PONs incorporating SSMF systems utilizing simple intensity modulation and

direct detection (IMDD).

To exploit the feasibility of WDM-PONs incorporating colorless REAM-based ONUs, we

have experimentally achieved 10Gb/s real-time end-to-end transmissions of single-band

OOFDM (SB-OOFDM) signals over 25km SSMF [19]. However, to further improve the

transmission capacity of a colorless REAM-based SB-OOFDM ONU in a cost-effective

approach, system designers face great challenges, as higher speed digital-to-analogue

converters (DACs) and analogue-to-digital converters (ADCs) are required, this makes it

difficult to avoid a prohibitive ONU transceiver cost. Another important issue to consider

when employing ultra-high sampling speed DACs/ADCs in the SB-OOFDM transceivers is

the escalation of the data bus capacity between the converters and the DSP logic circuits.

These ultra-high capacity data buses can be challenging to implement when trying to meet

tight cost and power constraints.

By employing a multi-band OOFDM (MB-OOFDM) approach, where multiple OFDM

signals are frequency division multiplexed (FDM) in the electrical domain, virtually all the

aforementioned disadvantages associated with the SB-OOFDM approach are eliminated.

Firstly, the bandwidth requirements of key components such as DACs/ADCs are dictated

only by the sub-band bandwidth and are no longer dependent on the total system capacity.

The increased flexibility in component choice can be highly beneficial for greatly lowering

the ONU transceiver cost. Secondly, by careful selection of the sub-band transmission

capacity, the ONU performance can be designed to meet the required peak user transmission

capacity whilst maintaining sufficient intra-band DBA functionality. In addition, MB-

OOFDM also has the salient advantage of significantly reducing transceiver complexity in

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Received 22 Jan 2013; revised 28 Mar 2013; accepted 2 Apr 2013; published 5 Apr 2013

8 April 2013 | Vol. 21, No. 7 | DOI:10.1364/OE.21.009167 | OPTICS EXPRESS 9169

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19.25Gb/s双频无色OOFDM在25km SSMF IMDD系统中的创纪录实测

在25 km SSMF IMDD系统上实现创纪录的高REAM强度调制器的19.25Gb / s实时端到端双频OFDM无色传输的实验演示

短程IMDD系统中1024-QAM OFDM发射机的实时演示

25km SSMF IMDD系统上创纪录19.25Gb/s双频OOFDM无色传输实验

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基于混沌序列的数据安全置乱IMDD-OFDM加密系统

IMDD-OQAM-OFDM系统中基于非参数直方图估计的低分辨率性能优化

同时估计信道和减轻IMDD-OQAM-OFDM系统内在虚像干扰的低开销均衡算法

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