Cartwright, 20, appeared at right-back during pre-season in games against Blackpool and Ashington.
He made 32 appearances for the Black Cats U21 side last season and as the son of former Spartans midfielder Peter Cartwright, should know all about the Croft Park club’s proud history and fans.
Otte, who also appeared for Spartans in pre-season, has played all over the world, the 24-year-old counting Bayer 04 Leverkusen U23s, Carolina Railhawks in the USA and New Zealand’s Western Suburbs among his former clubs.
He has now been granted international clearance after initially agreeing to join the promotion-chasing squad of Spartans manager Tom Wade last week.
Wade was happy to see the pair put pen-to-paper on Monday with the top flight campaign underway and Blyth's 1-0 win at Barwell on the opening day of the season.
Wade, pictured celebrating his side's win over Hartlepool United in the FA Cup last season, said: “It’s great to get the two lads in and both have come along with great pedigree.
“Fabian has been at Bayer Leverkusen, along with a number of other German clubs and he is a confident lad. He is very vocal and he will be fighting for his place along with Adam McHugh once Nick Thomson goes to America in a couple of weeks.
“Andrew almost joined a Football League club in the last couple of weeks and it was very much a touch and go situation. He has signed for us now and he fits into the ethos we have here.
“He is young, hungry and ambitious and coming from Sunderland’s academy, like Tom McNamee, we know he has a good upbringing.”
The Spartans manager added: “He is also the son of Peter Cartwright, who Spartans fans loved in his time at the club and it means he knows a bit about the club. Both can have great futures here at Blyth Spartans.”
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