I've used a laser cleaner, I also googled firmware but couldnt find anything for it.
I cleaned the laser lens of my ODD using cotton wool tip and alcohol and this worked like a charm. In your case its worth a try too.
Furthermore if an ODD firmware would be available, then you should find this on the Toshiba European driver page.
I checked it but did not find a firmware for TS-L633… so this means that firmware update is not necessary.
But be careful: the document contains different firmware files for different TS-L633 ODDs. If your ODD is not part of the list, don’t try to update the firmware since the usage of not compatible firmware would damage your ODD!!!