PDO query to IBM AS400 (sql) returns strange chars on fetchAll()

Question

I'm querying ibm as400 system (sql). When a value has special chars it returns like "IDSUNM" => b"Çamsan". Can't understand whats the b" before the actual value. When the value doesn't have special chars, it returns OK, "IDSUNM" => "A definir".

Functions that connects to sql:

protected function connection_as400($query = null)
{
    // Try to open a connection
    try {

        $params = "odbc:DRIVER={".config('database.connections.as400.driver')."}; SYSTEM={".config('database.connections.as400.host')."}; DATABASE={".config('database.connections.as400.database')."}; UID={".config('database.connections.as400.user')."}; PWD={".config('database.connections.as400.password')."};charset=utf8;";
        //dd($params);
        $as400_connection = new PDO($params);
        return $as400_connection;

        // If we can't establish a connection, show error...
    } catch (PDOException $e) {

        $as400_connection = null;
        dd($e->getMessage());
    }

    return 0;
}

How I'm quering the system:

$as400_connection = $this->connection_as400();
$query = $as400_connection->query("SELECT IDSUNO, IDSUNM FROM MVXBDTA.CIDMAS WHERE IDCONO = 1");
$results = $query->fetchAll(PDO::FETCH_ASSOC);

Results:

1 => array:2 [▶
    "IDSUNO" => "1804"
    "IDSUNM" => b"Çamsan"
]
5 => array:2 [▶
    "IDSUNO" => "*"
    "IDSUNM" => "A definir"
]

Thanks for any help given.