A graded-index plastic optical fiber (GI POF) with a high bandwidth and flexibility is expected to be a transmission medium for short-reach communication in home networks. However, the pluggable interconnects for consumers have not been emerged. Recently, we have developed ballpoint-pen interconnects where ball lens can be precisely mounted on GI POF end face using ballpoint-pen production technology, enabling easy connection, low-cost production, and fiber end face protection of GI POFs. Here, data transmission quality through coupled GI POFs with the ballpoint-pen connector is investigated. For evaluating data transmission quality, we measured bit error rate versus received optical power (BER curve) for a connector separation of 1.5 mm in the ballpoint-pen interconnect. The result shows error-free transmission (BER<10-12) was achieved by using the ballpoint-pen interconnect whereas transmission quality was significantly deteriorated by using the butt-coupling which is generally physically-contacted without fiber separations. This achievement with the ballpoint-pen interconnect may result from little dependence of the coupling loss on the connector separation because of the collimated output beam from GI POF with the ballpoint-pen connector. Furthermore, even for same received optical powers in the BER curve, the butt-coupling has worse transmission quality than the ballpoint-pen interconnect. This may result from some noises such as modal noise which occurs in multimode fiber connection as fluctuations of the coupling power. These results suggest that the ballpoint-pen interconnect is suitable for a consumer applications where the pluggable interconnects are essential. In the conference, the connector separation dependence of transmission quality through ballpoint-pen interconnect will be discussed.