constant difference meaning in English

不变的, 恒定的
常数, 恒量

To illustrate the superiority of this type of transition , the author adapted the local normal mode ( lnm ) based on couple - mode theory to explain the coupling between two lowest order modes along the transition . for the two important parameters , propagation constants difference between the two modes apy and mode coupling coefficient cy , which denoting power coupling between lnms , the approximation expressions using structure parameters were worked out . then the author compared three typical different transitions according to the demanding of power coupling , at last concluded that the parabolic - type transition can transport the light in shortest length with lowest loss
对于表征局部标准模之间功率耦合的两个重要的参数_ ( ij ) (模式传播常数差)和c _ ( ij ) (模式耦合系数) ，推导了用器件结构参数表达的近似公式，然后根据功率耦合的需求，在常见的三种不同轮廓的过渡区之间进行了比较，得出了抛物形轮廓过渡区能够使光束在最短尺寸内以最低损耗通过波导的结论。