Optical Cable Corp. of Roanoke, VA, has received $300,000 in initial stock orders from two Korean distributors. One order, worth $200,000, is from Daeho Netizens Co., a communications subsidiary of Daeho Corp., a Korean conglomerate based in Seoul. The order was for a full line of optical-cable products to be used in shipbuilding, cable TV, automotive, trucking, and general contracting markets. According to Robert Koptstein, Optical Cable Corp.`s president and chief executive, the order is the largest it has ever received from a distributor.