Chatsworth-based MRV Communications, a manufacturer of networking equipment and optical components, said Monday that it has received a warning letter from the NASDAQ. The firm said the NASDAQ Staff Determination letter indicates that the firm is not currently in compliance with NASDAQ listings requirements. The warning is a result of the delay in filing 10-Q reports for the firm's quarter ended June 30th, and is the first step in delisting procedures for the NASDAQ. MRV said in July that it would delay filing due to an investigation into the firm's historical stock option grant practices. According to MRV, it will initiate an appeal before the NASDAQ Listing Qualifications Panel.