Two arms of the interferometer are different in length by one -quarter of a guide wavelength, allowing the device to operate at its optimal linearity point without external electrical bias.

干涉仪的两个臂长相差波导波长的四分之一，使器件在最佳线性点工作，无需外加电偏压。

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In the US, political action committees (PACS) which are at arms length from the parties and candidates, are right in the thick of campaigning.

BBC: Funding merry-go-round shows no sign of stopping