An apparatus, comprising: a first input port ; a first switch , in optical communication with the first input port and switchable between a first state to pass optical signals and a second state to block optical signals; a second switch , in optical communication with the first input port and switchable between the first state and the second state; a second input port ; a third switch , in optical communication with the second input port and switchable between the first state and the second state; a fourth switch , in optical communication with the second input port and switchable between the first state and the second state; a first combiner in optical communication with the first input port via the first switch and the second input port via the third switch; a second combiner in optical communication with the first input port via the second switch and the second input port via the fourth switch; and a controller , operatively coupled to the first switch, the second switch, the third switch, and the fourth switch, to control the apparatus between a first operation mode, a second operation mode, and a third operation mode, in the first operation mode, the first switch being configured in the first state, the second switch being configured in the second state, the third switch being configured in the second state, and the fourth switch being configured in the first state, in the second operation mode, the first switch, the second switch, the third switch, and the fourth switch being configured in the first state, in the third operation mode, the first switch, the second switch, the third switch, and the fourth switch being configured in the second state. a first input port ; a first switch , in optical communication with the first input port and switchable between a first state to pass optical signals and a second state to block optical signals; a second switch , in optical communication with the first input port and switchable between the first state and the second state; a second input port ; a third switch , in optical communication with the second input port and switchable between the first state and the second state; a fourth switch , in optical communication with the second input port and switchable between the first state and the second state; a first combiner in optical communication with the first input port via the first switch and the second input port via the third switch; a second combiner in optical communication with the first input port via the second switch and the second input port via the fourth switch; and a controller , operatively coupled to the first switch, the second switch, the third switch, and the fourth switch, to control the apparatus between a first operation mode, a second operation mode, and a third operation mode, in the first operation mode, the first switch being configured in the first state, the second switch being configured in the second state, the third switch being configured in the second state, and the fourth switch being configured in the first state, in the second operation mode, the first switch, the second switch, the third switch, and the fourth switch being configured in the first state, in the third operation mode, the first switch, the second switch, the third switch, and the fourth switch being configured in the second state. <EOS>