Legal Question in Family Law in California

You may obtain such a subpoena from the court, but subpoenas are not filed.

Technically only the court can issue a subpoena of any kind. As officers of the court, licensed attorneys are authorized by statute to issue subpoenas under the power of the court. Non-attorney litigants, not being officers of the court, must have the court issue their subpoenas. Contact the court clerk's office in the court where your case is pending to find out what procedures they want you to follow to have a subpoena issued. (As Mr. White notes, subpoenas are "issued" not "filed.")