The Bank of Japan could raise interest rates twice by March, according to an ex-official, a prospect that may strengthen the yen and ripple through global markets. The potential move matters beyond Japan because a firmer yen can pressure carry trades, in which investors borrow in low-yielding currencies to fund purchases of higher-yielding or riskier assets elsewhere. If those positions begin to unwind, volatility can spread across foreign exchange markets and risk assets more broadly.