Spirent Communications saw half-year profits plunge as revenue declined on a lower order book.The communications technology company posted an adjusted operating profit of $18.2m, down from $59.1m the previous year, reflecting a drop in revenues and increased investment in product development.Revenue fell to $190.4m from $236.1m as the order book declined at the start of the year and as customers showed caution in near-term capital spending. Adjusted basic earnings per share tumbled to $0.02 from $0.06.Bill Burns, Chief Executive Officer, said: "Uncertainty and volatility in demand exhibited by our major customers in the first half resulted in near term challenges in trading. "However, we were encouraged by the improvement in order intake for the second quarter. "We believe the developments we are undertaking in new technology areas will deliver on-going and long term competitive advantages for Spirent."The company raised its dividend by 10% to $0.015 per ordinary share.Shares rose 5.30% to 139.10p at 10:52 on Thursday. RD