We　describe　a　synchronously-pumped　optical　parametric　oscillator　(OPO)　based　on　periodically　poled　KTiOPO(4)　(PPKTP).　The　OPO　was　pumped　by　a　self-mode-locked　Ti:sapphire　laser.　Its　signal　wave　covers　from　1070　nm　to　1375　nm,　and　could　be　tuned　freely　by　cavity-length　tuning,　the　corresponding　idler　wave　covering　from　1.9　mu　m　to　3.2　mu　m　in　the　mid-infrared　region.　Red,　green　and　blue　visible　light　were　also　generated　by　intra-cavity　sum　frequency　or　frequency　doubling.　The　threshold　was　measured　to　be　about　250　mW　at　810　nm　pump.　A　thin　glass　substrate　was　inserted　to　the　cavity　for　output　coupling,　and　the　maximal　output　power　was　measured　to　be　26　mW.　We　adopted　ring　cavity　and　linear　cavity　experimentally.　After　optimization,　the　output　characteristics　of　the　ring　cavity　and　linear　cavity　were　investigated　respectively.　The　approach　to　improve　the　output　efficiency　was　also　discussed.