A repeater amplifier assembly comprising: a first chassis containing first optics and electronics; a second chassis containing second optics and electronics; and a size adjustment mechanism connecting the first and second chassis (501, 502), and configured to adjust a size of the repeater amplifier assembly by reversibly adjusting a position of the first chassis with respect to the second chassis; wherein the size adjustment mechanism comprises a first mechanism that comprises: a guide rod that is left hand threaded at a first portion, and right hand threaded at a second portion; a first guide piece that is threaded on the left hand threaded portion; a second guide piece that is threaded on the right hand threaded portion, a mechanism for permitting the guide rod to be rotated with respect to the first and second guide pieces (602A, 602B) such that when the guide rod is rotated in a first direction, the first and second guide pieces (602A, 602B) move closer together along the guide rod, and such that when the guide rod is rotated in a second direction, the first and second guide pieces (602A, 602B) move further apart along the guide rod; a first reaction block slidably coupled to the guide rod; a second reaction block also slidably coupled to the guide rod; a resilient compression mechanism coupled to urge the first and second reaction blocks apart (603A, 603B) along the guide rod, wherein when the first and second guide pieces (602A, 602B) move closer together along the guide rod, the first and second guide pieces (602A, 602B) force the first and second reaction blocks (603A, 603B) to slide closer together along the guide rod and compress the resilient compression mechanism, and wherein when the first and second guide pieces (602A, 602B) move farther apart along the guide rod, the first and second guide pieces (602A, 602B) permit the resilient compression mechanism to push the first and second reaction blocks (603A, 603B) to be pushed further apart along the guide rod; and a force transfer mechanism configured to transfer output pressure on the first and second chassis (501, 502) when the first and second reaction blocks (603A, 603B) are moved further apart along the guide rod, and configured pull inward on the first and second chassis (501, 502) when the first and second reaction blocks (603A, 603B) are moved closer to each other along the guide rod. a first chassis containing first optics and electronics; a second chassis containing second optics and electronics; and a size adjustment mechanism connecting the first and second chassis (501, 502), and configured to adjust a size of the repeater amplifier assembly by reversibly adjusting a position of the first chassis with respect to the second chassis; a guide rod that is left hand threaded at a first portion, and right hand threaded at a second portion; a first guide piece that is threaded on the left hand threaded portion; a second guide piece that is threaded on the right hand threaded portion, a mechanism for permitting the guide rod to be rotated with respect to the first and second guide pieces (602A, 602B) such that when the guide rod is rotated in a first direction, the first and second guide pieces (602A, 602B) move closer together along the guide rod, and such that when the guide rod is rotated in a second direction, the first and second guide pieces (602A, 602B) move further apart along the guide rod; a first reaction block slidably coupled to the guide rod; a second reaction block also slidably coupled to the guide rod; a resilient compression mechanism coupled to urge the first and second reaction blocks apart (603A, 603B) along the guide rod, wherein when the first and second guide pieces (602A, 602B) move closer together along the guide rod, the first and second guide pieces (602A, 602B) force the first and second reaction blocks (603A, 603B) to slide closer together along the guide rod and compress the resilient compression mechanism, and wherein when the first and second guide pieces (602A, 602B) move farther apart along the guide rod, the first and second guide pieces (602A, 602B) permit the resilient compression mechanism to push the first and second reaction blocks (603A, 603B) to be pushed further apart along the guide rod; and a force transfer mechanism configured to transfer output pressure on the first and second chassis (501, 502) when the first and second reaction blocks (603A, 603B) are moved further apart along the guide rod, and configured pull inward on the first and second chassis (501, 502) when the first and second reaction blocks (603A, 603B) are moved closer to each other along the guide rod.