Could optical signals be in the forms of sinusoidal,triangle and square?

electrical signals are in the forms of sinusoidal, square and triangle
can we have the same forms for optical signals?

Optical signals are not exactly electrical signals. We only intensity modulate using optical signals, (think of it as some sort of on-off keying. If its on, LED emits light which travels through a fibre to a photodiode, which converts it back to electrical signal.). So, if you use an electrical signal of some waveform as input to an electrical system, only the light intensity will vary according to the input signal. Its frequency doesn't change and its wave shape doesn't change. It is always an em wave . Hence.the light wave can't take those shapes. however, you can use those waves to intensity modulate a light signal.

I think light INTENSITY can have any pattern similar to what we have with electrical signals. Most LEDs and lasers are used in ON/OFF mode but also "linear" devices exist the intensity of which is proportional to the electrical input.
I only do not know if such feature can be used for some purpose. If you want an electrical signal output from an optical link to follow the input signal pattern, you can easily use modulation by pulse width or otherwise, without caring how light intensity exactly is.