Research on packaging technology of miniaturized high broad-band ROSA based on small signal equivalent circuit

The internal detailed configuration of the ROSA.

With the rapid growth of the data traffic for hyper-scale internet data centre, the demand for high speed optical transceiver modules to interconnect among the intra and inter data centres beyond 100 Gbit/s becomes strong. Due to the limited space of the high port density line card data network center, the optical transceivers modules with small form factor are required to increase port density of line cards in communication systems. Considering the maturity of the process, the hybrid integration technology that assemble various discrete components in an ultra-compact tube is proposed to ensure the yield of the device.

For packaging process of receiver optical subassembly (ROSA) modules, the microwave circuit usually contains two parts of a radio frequency circuit and a bias network on which many capacitors and resistors are mounted. If they are all installed in one circuit board, it will easily cause crosstalk and distortion of the electrical signals. To overcome this drawback, the research group led by Dr. Jianguo Liu from Institute of Semiconductors, Chinese Academy of Sciences, proposed a 3D microwave circuit which allows radio frequency (RF) signal and bias voltage to be isolated in physical space for compact packaging. The value of this work is the experimental three-dimensional assembly of the ultra-compact ROSA based on the high speed microwave modeling. The -3 dB bandwidths of four channels of the fabricated module are all up to 20 GHz and the frequency response results are in very good agreement between the modeling and the experimental measurements. The results will extend our knowledge on hybrid-integrated technology. This work entitled Ultra-compact four-lane hybrid-integrated ROSA based on three-dimensional microwave circuit design has been published in Chinese Optics Letters, Vol. 17, Issue 3, 2019.

"The module used not only for 4×25 Gb/s non-return to zero (NRZ) modulation transmission, but also for many RF transmission systems such as remote antennas, satellite antennas, and secure encrypted communication. In addition, it can also be applied to radar systems to achieve full-band detection of radar"said Dr. Jianguo Liu from the research group.

With the multi-faceted application of detectors in radio-over-fiber (ROF) systems and digital center systems, detector modules will move toward high power output, high signal-to-noise ratio, miniaturization, integration, and low power consumption. The further work will focus on the integration of detector chips with other functional chips, such as semiconductor optical amplifier (SOA) chips, trans-impedance amplifier (TIA) chips, and development of multi-function devices.

基于等效电路的小型化宽频带接收模块封装技术研究

集成小型化接收模块内部结构图。

随着超大规模互联网数据中心流量的快速增长，内部数据中心对100 G高速光模块提出了很高的需求。由于高端口密度线卡数据网络中心的空间有限，为增加通信系统中线卡的端口密度，内部光收发模块需要具有小型化的特点。考虑到目前芯片制作工艺的成熟度，通常采用混合集成技术将各个功能器件组装在超紧凑的管壳中，以确保器件的良率。

对于光接收组件(ROSA)模块的封装过程，其微波电路通常包含射频电路和偏置网络两部分，偏置网络中需要配很多电容和电阻。如果将射频电路和偏置网络都在一块电路板上实现，将很容易引起电信号的串扰和失真。为了克服这个缺点，由中国科学院半导体研究所刘建国研究员领导的研究小组提出了一种3D微波电路，它将射频（RF）信号和偏置电压在物理空间上进行隔离，同时也实现了小型化封装。这项工作的价值在于建立了接收模块的分布式小信号等效电路模型，并分析了封装过程中寄生参数的影响，模型的仿真结果和实验测量结果拟合度很好。所研制的探测器接收模块每个通道的-3 dB带宽均高达20 GHz。这一结果拓展了人们对混合集成技术的了解。相关研究结果以“Ultra-compact four-lane hybrid-integrated ROSA based on three-dimensional microwave circuit design”为题发表于Chinese Optics Letters 2019年第17卷第3期。

该团队的刘建国研究员认为：“该模块不仅可以用于4×25 Gb/s 非归零码（NRZ）调制传输，还可用于许多RF传输系统，如远程天线、卫星天线、安全加密通信等。此外，它还可以应用于雷达系统，实现全波段雷达检测“。

随着探测器在光载无线通信（ROF）系统和数字中心系统中多方面的应用，探测器模块将向高功率输出，高信噪比、小型化、集成化和低功耗方向发展。接下来，该研究团队将重点关注探测器芯片与其他功能芯片比如半导体光放大器（SOA）芯片、互阻放大器（TIA芯片）等芯片的集成，实现多功能器件的开发。