An optical system comprising: at least one cable landing stations,CLS, coupled to a first trunk path, the first trunk path including at least a first trunk path cable segment and a second trunk path cable segment, each of the first and second trunk path cable segments (114-3, 114-4) comprising an undersea cable having at least one electrical conductor, respectively; and at least one power feed branching unit,PFBU, located in an undersea environment coupled between the first and second trunk path cable segments (114-3, 114-4), the PFBU having a DC/DC converter,DDCM, arrangement (501/518) with a first port to electrically couple to the at least one electrical conductor of the first trunk path segment, a second port to electrically couple to the at least one electrical conductor of the second trunk path segment, and a third port to electrically couple to an electrical conductor of a branch path cable segment, characterised in that: the DDCM arrangement is configured to maintain a constant output current level via the second port based at least in part on a first input current received via the first port coupled to the at least one electrical conductor of the first trunk path segment and a second input current received via the third port coupled to the electrical conductor of the branch path cable segment. at least one cable landing stations,CLS, coupled to a first trunk path, the first trunk path including at least a first trunk path cable segment and a second trunk path cable segment, each of the first and second trunk path cable segments (114-3, 114-4) comprising an undersea cable having at least one electrical conductor, respectively; and at least one power feed branching unit,PFBU, located in an undersea environment coupled between the first and second trunk path cable segments (114-3, 114-4), the PFBU having a DC/DC converter,DDCM, arrangement (501/518) with a first port to electrically couple to the at least one electrical conductor of the first trunk path segment, a second port to electrically couple to the at least one electrical conductor of the second trunk path segment, and a third port to electrically couple to an electrical conductor of a branch path cable segment, characterised in that: the DDCM arrangement is configured to maintain a constant output current level via the second port based at least in part on a first input current received via the first port coupled to the at least one electrical conductor of the first trunk path segment and a second input current received via the third port coupled to the electrical conductor of the branch path cable segment. environment coupled between the first and second trunk path cable segments (114-3, 114-4), the PFBU having a DC/DC converter,DDCM, arrangement (501/518) with a first port to electrically couple to the at least one electrical conductor of the first trunk path segment, a second port to electrically couple to the at least one electrical conductor of the second trunk path segment, and a third port to electrically couple to an electrical conductor of a branch path cable segment, characterised in that: the DDCM arrangement is configured to maintain a constant output current level via the second port based at least in part on a first input current received via the first port coupled to the at least one electrical conductor of the first trunk path segment and a second input current received via the third port coupled to the electrical conductor of the branch path cable segment.