光电工程, 2010, 37 (8): 145, 网络出版: 2010-09-07
VOA指定衰减点零坡度的实现
VOA with Flattened Slope at Assigned Points
摘要
EDFA 系统中要求VOA 在光衰减1 dB 时光功率对控制电压的曲线斜率小于1 dB/V,绝大部分VOA 均不能满足此项要求。改变放大增益的传统方法是采用输出反馈分级控制运放增益,但不足之处是增益曲线存在不连续点。我们采用纯模拟非线性电路巧妙地实现了这个要求,很好地降低了在特定点增益曲线的坡度,衰减曲线除在1 dB 附近变为平坦外,其余均保持了原来的数值,并且曲线无任何不连续点。文中进行了理论分析,并用CadenceOrcad Pspice 软件对电路进行了仿真和分析,求出了零坡度(曲线导数为零)所需要的条件。同时分析了同一型号JFET 和MATT VOA 的离散性,和温度变化带来的影响。采用此项技术,电路所占空间极小,成本较低,成功地做出了符合要求的8 个VOA 样品,并列出了各种电的和光的测试结果。
Abstract
The slope of the curve optical power VS. voltage at ATT=1 dB is required to be less than 1 dB/V, which is not met by most of VOA. The traditional method is to control the gain of multi-stage operational amplifiers by the output feedback. However, the discontinuity points on gain curve are inevitable. Based on the pure non-linear circuit, the requirement can be met. Besides flattening the slope @ATT=1 dB at specific points, the curve still keeps the original value and there is not any discontinuous points. The theory is analyzed, the circuit is simulated by Cadence Orcad Pspice software,and the conditions of zero slope the derivative of the curve is zero) are derived. The diversity of JFET and MATT VOA is analyzed and the temperature characteristics are investigated. Based on the technique above, the circuit occupies small space and its cost is low, 8 pcs MATT VOA modules are made successfully and the optical and electrical test results are shown.
王伟. VOA指定衰减点零坡度的实现[J]. 光电工程, 2010, 37(8): 145. WANG Wei. VOA with Flattened Slope at Assigned Points[J]. Opto-Electronic Engineering, 2010, 37(8): 145.