Mid-plane mounted optical communications system and method for providing high-density mid-plane mounting of parallel optical communications modules

An optical communications system comprising:

• a motherboard comprising a substrate having an upper surface and a lower surface, the upper surface having at least two arrays of electrical contact pads disposed thereon, the substrate having electrical conductors extending through the substrate;
• at least first and second hub integrated circuits (ICs) mounted on the upper surface of the motherboard and electrically connected to one or more of the electrical conductors that extend through the motherboard substrate;
• at least X Meg-Array connector assemblies, each Meg-Array assembly comprising a Meg-Array receptacle and a Meg-Array plug that are mechanically and electrically coupled to each other, where X is an integer that is equal to or greater than 48, the lower and upper surfaces of the receptacle and the plug, respectively, having respective ball grid array (BGAs) thereon, wherein the Meg-Array connector assemblies are mounted on the upper surface of the motherboard such that the arrays of electrical contact pads on the upper surface of the motherboard are in electrical contact with the respective BGAs of the respective receptacles;
• and
• at least X parallel optical communications modules (POCMs), each POCM having at least a front side, a back side, a bottom side, and a top side, the POCMs being mounted on the upper surfaces of respective ones of the Meg-Array plugs, the POCMs and the respective plugs on which the POCMs are mounted being arranged on the upper surface of the motherboard in groups with each group comprising at least a front POCM and a back POCM, and wherein the back side of the front POCM of each respective group is in contact with or in close proximity to the front side of the back POCM of the same respective group such that the back side of the front POCM of each respective group is spaced a spacing distance, DS, from the front side of the back POCM of the same respective group, wherein DS is equal to or greater than 0 millimeters (mm) and less than or equal to about 15 mm, and wherein each POCM is connected to a proximal end of a respective optical fiber ribbon cable in such a way that the respective cables exit the respective POCMs from the back sides of the respective POCMs.

A method for performing parallel optical communications in an optical communications system, the method comprising:

• providing a motherboard comprising a substrate having an upper surface and a lower surface, the upper surface having at least X arrays of electrical contact pads disposed thereon, where X is a positive integer that is equal to or greater than 2, the substrate having electrical conductors extending through the substrate, the upper surface of the motherboard having at least first and second hub integrated circuits (ICs) mounted thereon, the hub ICs being electrically connected to one or more of the electrical conductors that extend through the motherboard substrate, the upper surface of the motherboard having X Meg-Array receptacles mounted thereon, each Meg-Array receptacle having a ball grid array (BGA) thereon that is in electrical contact with a respective one of the arrays of electrical contact pads disposed on the upper surface of the motherboard;
• and
• providing X Meg-Array plugs having X parallel optical communications modules (POCMs) mounted thereon, respectively, each POCM having at least a front side, a back side, a bottom side, and a top side, the POCMs and the respective plugs on which the POCMs are mounted being arranged on the upper surface of the motherboard in groups with each group comprising at least a front POCM and a back POCM, and wherein the back side of the front POCM of each respective group is in contact with or in close proximity to the front side of the back POCM of the same respective group such that the back side of the front POCM of each respective group is spaced a spacing distance, DS, from the front side of the back POCM of the same respective group, wherein DS is equal to or greater than 0 millimeters (mm) and less than or equal to about 15 mm, and wherein each POCM is connected to a proximal end of a respective optical fiber ribbon cable in such a way that the respective cables exit the respective POCMs from the back sides of the respective POCMs.