Typical light path 1:

BS is a nonpolarized beam splitter; polarizer angle can be horizontal or vertical; polarizer angle is orthogonal to polarizer . If the laser is linearly polarized, a half wave plate can be used to replace the polarizer.

Typical light path 2：

PBS polarizing prism is used to replace the polarizer, s light is vertically polarized into the modulator, and P light is horizontally polarized out.

Typical light path 3：

BS is a nonpolarized beam splitter; polarizer angle can be horizontal or vertical; polarizer angle is orthogonal to polarizer.

Typical light path 4：

The incident angle is as small as possible (generally less than 5 °), the angle of the polarizer is horizontal or vertical, and the angle of the polarizer is orthogonal to the polarizer.
Similarly, if the laser emits linearly polarized light, a half wave plate can be used instead of the polarizer.