Identifying Fixed Income Credit Strategies

James is a portfolio manager tasked with developing a strategy to enhance the yield of a fixed income portfolio that comprises corporate bonds. He is considering a range of credit strategies, emphasizing the evaluation of creditworthiness and potential risk premiums of different issuers.

One common strategy involves investing in bonds that carry a lower credit rating but offer higher yields compared to their higher-rated counterparts. This strategy can potentially lead to higher returns, but it also comes with increased risk.

What is this strategy called?