By MILT SOSIN

Convicted Cuban exile terrorist Humberto Lopez was sentenced to a 15-year state prison term today for violating his probation and possessing explosives which blew off part of his hand and blinded him in one eye.

Lopez' supporters who packed the courtroom were stunned by the severity of the sentence and burst into loud singing of the Cuban National Anthem after the sentence was pronounced by Circuit Judge Arden Siegendorf.

The state prison term will be in addition to 4 1/2 year federal prison sentence Lopez received last week. His attorney asked that the sentences be made concurrent.

Lopez, his exile followers and his family and attorneys had expected a lighter sentence.

It was learned a harsh probation report on the defendant, which was not made public, may have figured in the stiff sentence.

Lopez was one of two exiles convicted of making a bomb that blew up in their hands in March, 1974.

Both Lopez and his companion, Luis Crespo, were severely injured by the blast. Crespo, who lost parts of both hands, was sentenced to five years in prison.

Lopez, who lost his left eye and three fingers of his left hand in the bomb explosion, received probation when he pleaded no contest and promised that he would engage in no criminal acts while free.

Instead, Lopgz fled to Santo Domingo from where he was quoted as issuing militant statements.

"His subsequent acts," testified assistant state attorney Robert Kaye, who took the stand in an unusual move, "are a slap in the face of this court.

"The defendant was given his liberty under this pledge, and he then thumbed his nose at the court," Kaye said. "To permit him to get away with such actions would constitute an open invitation to anyone to engage-in a similar act."

Before the sentence was pronounced, Lopez addressed the court through an interpreter, saying "I have the utmost confidence in the fairness of this court and in the American judicial system and those are the things I am fighting for for my own homeland."

Judge Siegendorf said "My heart remains for the Cuban people, as I said in sentencing the co-defendant in this case.

"But this court will not tolerate acts directed against the United States and the people of this country," the judge said.

Then, in passing sentence, Siegendorf said, "I am taking judicial notice that this defendant was abroad on in custody at the time of the recent wave of bombing terrorism, so that the sentence no way reflects any accountability on the part of Mr. Lopez for those acts."

He then pronounced the prison sentence and Lopez, who understands English fairly well, shook his head in disbelief.